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In an open type wind tunnel experiment of flow over a bluff body (bluff body is kept in wind tunnel test section), initially without the bluff body the velocity was calculated and this velocity is used for calculating Cd and Cl. Presence of the bluff body obviously increases the blockage and the velocity reduces in the test section. Does it make sense if we calculate the velocity with the presence of the bluff body and this reduced velocity value is used for further calculations?
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why don't you check with blockage corrections in automotive wind tunnel? The blockage problem should not be reduced to the jet expansion effect alone. There is a nozzle effect, a collector effect and a static pressure gradient effect of the empty test section as well (see SAE Technical Paper Series).
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Dear All,
Coagulating (aggregating, coalescing) systems surround us. Gravitational accretion of matter, blood coagualtion, traffic jams, food processing, cloud formation - these are all examples of coagulation and we use the effects of these processes every day.
From a statistical physics point of view, to have full information on aggregating system, we shall have information on its cluster size distribution (number of clusters of given size) for any moment in time. However, surprisingly, having such information for most of the (real) aggregating systems is very hard.
An example of the aggregating system for which observing (counting) cluster size distribution is feasible is the so-called electrorheological fluid (see https://www.youtube.com/watch?v=ybyeMw1b0L4 ). Here, we can simply observe clusters under the microscope and count the statistics for subsequent points in time.
However, simple observing and counting fails for other real systems, for instance:
  • Milk curdling into cream - system is dense and not transparent, maybe infra-red observation could be effective?
  • Blood coagulation - the same problem, moreover, difficulties with accessing living tissue, maybe X-ray could be used but I suppose that resolution could be low; also observation shall be (at least semi-) continuous;
  • Water vapor condensation and formation of clouds - this looks like an easy laboratory problem but I suppose is not really the case. Spectroscopic methods allow to observe particles (and so estimate their number) of given size but I do not know the spectroscopic system that could observe particles of different (namely, very different: 1, 10, 10^2, ..., 10^5, ...) sizes at the same time (?);
  • There are other difficulties for giant systems like cars aggregating into jams on a motorway (maybe data from google maps or other navigation system but not all of the drivers use it) or matter aggregating to form discs or planets (can we observe such matter with so high resolution to really observe clustering?).
I am curious what do you think of the above issues.
Do you know any other systems where cluster size distributions are easily observed?
Best regards,
Michal
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Dear Johan!
I want to recommend you papers of my husband)) He study aggregation of blood particals by scanning flow cytometry and also produced (I think, new and fruitfull) kinetic model for this processes. It is his profile https://www.researchgate.net/profile/Vyacheslav-Nekrasov
As I understand, key papers is
1 Brownian aggregation rate of colloid particles with several active sites
2 Kinetic turbidimetry of patchy colloids aggregation: latex particles immunoagglutination
3 Mathematical modeling the kinetics of cell distribution in the process of ligand–receptor binding
4 Kinetics of the initial stage of immunoagglutionation studied with the scanning flow cytometer
But you can write him directly))
Best wishes, Anna
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I am using the experimental scheme presented in the image below. It seems that no matter what I do, I cannot obtain coincidence counting higher than 350/s, although the single count at each detector is about 500000/s. The crystal used is a 2 cm long 10 um period PPKT collinear type II crystal.
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I would suggest to verify the temporal synchronization of the two detectors. For a too narrow coincidence window and different latency of the detectors, the true coincidences might be outside of the coincidence window. Only false (random) coincidences are present. The first step would be to increase the coincidence window to dozens of ns to surely cover any difference in latency. Then you can start decreasing the coincidence window and adding a delay to the fastest detector channel, e.g. using time tagger functionality or simply extending the length of a coaxial cable.
Also, it might be useful to add cut-off filters transmitting the red signal and stopping the blue pump in front of the detectors. Using the filters you make sure that your signal comes from the SPDC process and not from the laser. Filters https://www.semrock.com/filterdetails.aspx?id=blp01-633r-25 are very good but you can use any low-cost alternative.
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I have the energy specter acquired from experimental data. After normalization, it can be used as a probability density function(PDF). I can construct a Cumulative distribution function(CDF) on a given interval using its definition as the integral of PDF. This integral simplified as a sum because of the PDF given in discrete form. I want to generate random numbers from this CDF.
I used Inverse transform sampling replacing CDF integral with sum. From then I am following the standard routine of the Inverse transform sampling solving it for sum range instead of an integral range.
My sampling visually fits experimental data but I wonder if this procedure is mathematically correct and how it could be proofed?
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The ideas are ok but you need to do things that show your summs converge to the integral. Referring to a text on harmonic analysis or numerical analysis would probably be beneficial.
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I'm looking for a lab lab-scale gas compressor, having high output pressure up to 100 bar but small flow (up to several litres per h). I've found that a membrane pump could be used in such applications, but unfortunately the source document lacks any details.
Is anybody familiar with such applications? Could it be a typical diaphragm dosing pump just running dry?
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Due to the high pressure and low flow requirements, you should theoretically choose a reciprocating or piston compressor.
In Jansohn, Peter. (2013). Modern Gas Turbine Systems: High Efficiency, Low Emission, Fuel Flexible Power Generation. Oxford. Woodhead Publishing Limited, you can find a guide on how to choose a compressor according to pressure and flow parameters.
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Journal of Multidisciplinary Applied Natural Science (abbreviated as J. Multidiscip. Appl. Nat. Sci.) is a double-blind peer-reviewed journal for multidisciplinary research activity on natural sciences and their application on daily life. This journal aims to make significant contributions to applied research and knowledge across the globe through the publication of original, high-quality research articles in the following fields: 1) biology and environmental science 2) chemistry and material sciences 3) physical sciences and 4) mathematical sciences.
We invite the researcher related on our scope to join as section editor based on their interest or as regional handling editor in their region. The role of editor is help us to maintain and improve the Journal’s standards and quality by:
  1. Support the Journal through the submission of your own manuscripts where appropriate;
  2. Encourage colleagues and peers to submit high quality manuscripts to the Journal;
  3. Support in promoting the Journal;
  4. Attend virtual Editorial Board meetings when possible;
  5. Be an ambassador for the journal: build, nurture, and grow a community around it;
  6. Increase awareness of the articles published in the journal in all relevant communities and amongst colleagues;
  7. Regularly agreeing to review papers when invited by Associate Editors, and handle these promptly to ensure fast turnaround times
  8. Suggest referees for papers that you are unable to review yourself
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Frank T. Edelmann yes sure, thanks for your good discussion. we create this journal based on the other multidisciplinary journal, as example Journal of King Saud University - Science (scopus indexed) publishes peer-reviewed research articles in the fields of physics, astronomy, mathematics, statistics, chemistry, biochemistry, earth sciences, life and environmental sciences.
Other example, PERIÓDICO TCHÊ QUÍMICA (scopus indexed) also publishes peer-reviewed research article in same fields with our journal.
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The Energy plus documentation (input/output) specifies that for typical commercial buildings in the USA, a reasonable default value for ground temperature: building surface is 2 degC less than the average indoor space temperature. And a practician in 2011 mentions that he has seen many simulations doing simplified method:
- using the last month's mean temperature, less 1 degree.
Similar to the Energy+ O/I documentation and Aside from applying:
  • Auxiliary programs that can be simulated independent of the IDF file and determine detailed ground heat exchange ------ Ground heat transfer modeling " with "kiva"
  • Ground Temperature Calculation through a Basement\slab Calibration process.
- What is the best and easiest (more abstract) method, to input reasonable default values as a ground monthly temperature for small/large residential building models?
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thank you so much for your kind information@ Adel Boumerzoug
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can anyone guide me about the Journals, basically I want to publish my paper and I want to publish my paper in a 5,6 impact factor journal so please guide me in which journal is best.
In my paper, I have worked on an application with 5 different characterizations so is it possible my paper will be published in a 5,6 impact factor journal??
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Ait Mansour El Houssain thanks a lot for useful tips and guidance. After choosing the title of my paper i will share my experience with all of you thanks again
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how to spliced different different core size (MFD) fibres ( single mode to graded index multimode). I am trying to splice SMF to GIMF, to fabricate SMF-GIMF-SMF saturable absorber.
Although, I could splice with apparently no power loss (shows 0dB loss). However, splicer shows "Bubble Error", even after several attempts.
note:Please have a look at the photos attached
Thanks
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Hi Abbas
I have the same question! I am trying to fabricate SMF-GIMF-SMF structure for sensor application. I tried many times to splice the fibres. I manipulated with different splicer parameters as prefusion time, overlap, arc power and so on, but almost always I got splice with a black vertical line (fig. 1).
Once I got good splice. It happened when I accidentally broke the bad splice and respliced it again. Unfortunately, I could never repeat it.
At fig.2 you can see two spectrums. The blue one corresponds to SMF-GIMF-SMF with both bad splices. The red one corrensponds to SMF-GIMF-SMF that have one good splice. The second spectrum had a much better contrast then the first one. This is due to the fact that the modes in GIMF fibre are more equally coupled to the SMF fiber. Thus, there is a difference between coupling coefficients of modes in GIFM to SMF fibre for the "bad" and "good" splice.
P.S. Abbas, please, let me know if you will find a method, how to splice it without bubbles and black curves!:)
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I have three collimated optical beams with 1cm separation between the adjacent one. I want to shift one of the three beam laterally so that it goes closer towards or farther away from the adjacent beam by micrometer accuracy.
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Dear Sreeprasad
If you are not worried about relative phases and can tolerate a number of very weak secondary beams, perhaps the simplest way is to insert a tilted parallel glass plate into the beam you want to translate. The translation of the main transmitted beam will be Theta*T*(n-1)/n, where n is the refractive index of the glass plate, T is its thickness and Theta is the tilt of the plate's normal relative to the beam propagation direction (in radians). A 1 mm thick glass slide at 5 degrees will result in a shift on order of 50 microns. The main drawback from this method is that more than one beam is transmitted due to the multiple reflections at the glass surface, however the main transmitted beam will be several hundred times more intense than the strongest secondary beam.
Good luck
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We know that mathematicians study different mathematical spaces such as Hilbert space, Banach space, Sobolev space, etc...
but as engineers, is it necessary for us to understand the definition of these spaces?
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Yes, we do have to know about the spaces, at least during our university studies, to enables us to expand our mind into abstact level, that will be very usefull for design activities
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How to decide whether system is order and disorder in a ferro-electric perovskite oxide (ABO3 type ) using Raman spectroscopy
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Thank you very much Dr. Thomas Breuer and Dr. Alaa Faid .
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For example. The American philosopher Brand Blanshard wrote the eloquent Reason & Analysis (1962). At page 265 he wrote: "A priori truths may be recognized not only without the assistance of language, but without any traceable reference to it." Steven Pinker, in his 2000 book, The Language Instinct, puts it this way: "Grammar offers a clear refutation of the empiricist doctrine that there is nothing in the mind that was not first in the senses" (p. 117). The contrary view was taken by David Hume over 200 years earlier: “Tis impossible for us to carry on our inferences ad infinitum; and the only thing, that can stop them, is an impression of the memory or senses, beyond which there is no room for doubt or enquiry” (Book I, Part III, Section IV). Does the development of physics require empiricism?
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absolutely yes
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I prepared ZnO via a different method but I found something. I think it's a strange optical band gap.
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If you confirmed the formation of ZnO by different experimental tools and you found a decrease in the band gap relative to bulk Zno structure, then, the decrease in the band gap may arise from the formation of crystal defects like oxygen vacancies. You could confirm this interpretation by measuring the fluorescence spectroscopy.
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What is the best way one can measure the refractive index of different concentration for the same solution, i.e. silver nitrate AgNO3 in de-ionised water? Silver nitrate AgNo3 in different concentration, i.e. 100mg/l or 50mg/l.
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Not of direct help to the question asked, but I offer:
Langford, S. A., and J. K. Nakagawa, 1978. A general equation for estimating refractive indices of Cargille liquids at various temperatures and wavelengths. The Microscope, v. 26, no. 4, pp. 167 - 170.
&
Langford, S. A., 1991. A modified Jelley refractometer. The Royal Microscopical Society J. Microscopy, v. 163, pt. 3, September, pp. 333 - 345. [Please note that the equation on p. 339 requires addition of constant 1.517207, which was inadvertently lost due to an interruption during my final editing work. The correction was published in a later issue, which I can not locate on the Web. --SL, 20 Oct 2016] https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2818.1991.tb03184.x, tinyurl.com/ya9ahlc8.
For purposes of liquid-immersion refractometry [see, for instance, < https://tinyurl.com/yabku63f >] I think that there is no substitute for calibration of liquids soon before they are to be used. Better yet would be the development of an instrument that would continuously log Liquid RIs during liquid-immersion work.
I hope that these thoughts help at least some readers. :-)
-Steve-
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I am doing research on tin and tin oxide nanoparticles using laser ablation method. Using Nd:YAG  laser in visible range (532nm) .By increasing the energy  i have observed the  decrease in the ratio of number of oxides. What might be the reason?The sample exposure time is constant/
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@ Xxx Sedao : No, gas shielding alone won't do you any good with this problem as I explained earlier. The oxygen comes form the dissociation of SnO2 at high temperatures, so you create the oxygen by yourself. Hence, there will be oxygen around even if you work in an inert atmosphere.
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An atomic clock emits a nano-bullet that moves at a given speed through a vacuum pipe to another atomic clock at a given moment. The other atomic clock records the instant at which the bullet reaches and calculates the time of another atomic clock based on the known speed and distance. Sync the clock and repeat the back and forth comparisons. The data match shows that the clock time coincides.
With such a synchronous clock, can we measure the unidirectional speed of light unchanged?
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To the original question: the two-way speed of light can clearly be measured with no issues: a light beam goes from source A to mirror B at distance L and then back to source A. A clock at A measures the time elapsed and always finds 2L/c, with c independent of reference frame.
So far, this is experiment, well confirmed in many different ways.
One-way speed of light always has some kind of problem, since we need to say when two distant clocks mark the same time. It turns out that it is a consistent convention to assume that clocks can be synchronised in such a way as to make the one-way speed of light constant.
However, to make contact with those who mentioned the Sagnac effect, this consistency only holds in *inertial* reference frames, not in rotating ones. In rotating reference frames, or other non-inertial frames, you generally cannot consistently synchronise clocks in such a way as to have a constant one-way speed of light.
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I have heard that if you collapse a bubble in the water with some sort of sound wave it will produce light. Is it a special gas or just a bubble of air?And is it a special wave sound?
I wonder what the reason behind this phenomenon could be?
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Dear Mr.James Garry
It is just a personal interest,my major study is in a different field.
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What are the basic mechanisms or processes that occurs polarization in dielectrics?
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There are two types of dielectrics, polar and non-polar. Non-polar dielectrics do not have a permanent electric dipole moment, when you apply a field, you generate dipolar moments in the direction of the applied field. You can see the microscopic polarization (the response to the field), as the sum of all the dipolar moments induced. For polar dielectrics, when you applied a field, the pre-existent dipolar moments suffer a torque and tend to align with the applied field, in this case the polarization can now be seen as an average of all the dipoles orientations.
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Dear colleagues,
Without nonlinear absorption, the Z-scan curve corresponding to the pure nonlinear refraction will be symmetric around the origin O. The nonlinear absorption will lead to asymmetry of Z-scan curve. Thus, the closed aperture Z-scan of a material with nonlinear nonlinear absorption and nonlinear refraction give an asymmetric curve. Therefore, we can develop a matlab program to automatically generate nonlinear absorption curves so that these curves multiply with the closed aperture Z-scan curves reproduce a symmetric curve [1]. From this symmetry curve, we can calculate the nonlinear refractive indices, and from the nonlinear absorption curve produced by the matlab program we derive the nonlinear absorption coefficient without the open aperture Z-scan measurement. I have implemented the above idea on closed aperture Z-scan data in works [2] and [3] and found that results perfectly consistent with results in above works. In summary, we can use the matlab program or the numerical methods (fitting curve) generally to determine n2 and beta from the closed- aperture Z-scan data. But why in most works did open aperture Z-scan measurements implement to determine n2 and beta, are this measurements really necessary?
Thank you and hoping for your insightful response.
[2] Sheik-Bahae, M., Said, A. A., Wei, T. H., Hagan, D. J., & Van Stryland, E. W. (1990). Sensitive measurement of optical nonlinearities using a single beam. IEEE journal of quantum electronics, 26(4), 760-769.
[3] Abrinaei, F. (2017). Nonlinear optical response of Mg/MgO structures prepared by laser ablation method. Journal of the European Optical Society-Rapid Publications, 13(1), 15.
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I think when nonlinear refraction is dominant, you can extract the nonlinear parameters from the closed z-scan with some confidence. However, there are cases , for example when either NL refraction or absorption are dominant, that you cannot do that without ambiguity, so that is why it is customary to run the open z-scan to get the NL absorption parameters first, and then used them in the closed-aperture results. Experimentally all you need is a beam splitter in the far field, and an extra detector yo obtain both the open and closed-zscan traces at the same time
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Z-scan technique is very powerful and simple in determining both the sign and magnitude of the nonlinear refractive index  and the nonlinear absorption coefficient . The original Z-scan was proposed by Prof.Sheik- Bahae  et al in 1989 identifying nonlinear coefficients  and  through a closed  aperture Z-scan and an open aperture Z-scan1,2 . This method can be called transmittance based Z-scan. Since then, many variants of original Z-scan technique have been developed to enhance the sensitivity and signal-to-noise ratio. According Prof.T.Godin3, these variants can be categorized into 4 types: alteration of the input beam profiler4,5, theory optimization6, alteration of the detection system3,7-10  or modification of the original experimental setup11-14 .
However, when I read articles on the investigating third order nonlinear characteristics of material, the method often used is  Z-scan method of Prof.Sheik- Bahae. Why these variants are not applicable and can not replace the original Z-scan?
Thank you and hoping for your insightful response.
1.M.Sheik-Bahae,  A. A.Said, and E. W. Van Stryland, High-sensitivity, single-beam n2 measurements, Opt. Lett 14(17)  (1989)  955-957.
2.P. B. Chapple, J. Staromlynska, J. A. Hermann, T. J. Mckay, R. G. Mcduff, Single-Beam Z-Scan: Measurement Techniques and Analysis, J. Nonlinear Optic. Phys. Mat, 6(3) (1997) 251-293.
3.T.Godin, M.Fromager, E.Cagniot, R.Moncorgé and K. Aït-Ameur, Baryscan: a sensitive and user-friendly alternative to Z scan for weak nonlinearities measurements. Opt. Lett, 36(8) (2011) 1401-1403.
4.W. Zhao and P. PalffyMuhoray, Zscan technique using tophat beams, Appl. Phys. Lett. 63 (1993) 1613.
5.S. Hughes and J. M. Burzler, Theory of Z-scan measurements using Gaussian-Bessel beams, Phys. Rev. A 56(1997) R1103.
6.R. E. Bridges, G. L. Fisher, and R. W. Boyd, Z-scan measurement technique for non-Gaussian beams and arbitrary sample thicknesses, Opt. Lett. 20(1995)1821.
7.T Xia, M Sheik-Bahae, AA Said, DJ Hagan, Z-scan and EZ-scan measurements of optical nonlinearities, J. Nonlinear Optic. Phys. Mat,  3(04) (1994) 489-500.
8.A. O. Marcano, H. Maillotte, D. Gindre, and D. Métin, Picosecond nonlinear refraction measurement in single-beam open Z scan by charge-coupled device image processing, Opt.Lett. 21(1996)101.
9.G.Boudebs, V.Besse, C.Cassagne, H.Leblond, and F.Sanchez, Why optical nonlinear characterization using imaging technique is a better choice?, In: Transparent Optical Networks (ICTON), 2013 15th International Conference on. IEEE ( 2013) 1-4.
10.G.Tsigaridas, M.Fakis, I.Polyzos, P.Persephonis and V.Giannetas,  Z-scan technique through beam radius measurements, Appl. Phys. B  76(1)(2003) 83-86.
11.G. Boudebs and S. Cherukulappurath, Nonlinear optical measurements using a 4 f coherent imaging system with phase objects, Phys. Rev. A 69(2004) 053813.
12.D. V. Petrov, A. S. L. Gomes, and C. B. De Araujo, Reflection Z-scan technique for measurements of optical properties of surfaces, Appl.Phys. Lett. 65(1994)1067.
13.H. Ma and C. B. De Araujo, Two color Z-scan technique with enhanced sensitivity, Appl. Phys. Lett. 66(1995)1581.
14.A. A. Andrade, E. Tenorio, T. Catunda, M. L. Baesso, A. Cassanho, and H. P. Jenssen, Discrimination between electronic and thermal contributions to the nonlinear refractive index of SrAlF 5: Cr+ 3, J. Opt. Soc. Am. B 16(1999) 395.
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Dear Lam Thanh Nguyen:
Thank you for your question, which has introduced me to the Z-Scan technology of which I have previously been completely ignorant. I don't have time to become an expert in your field, but I have just glanced at
My own impression is that as a scientist it is your job to pursue the answers to such questions you have asked by designing your own investigations to achieve the results you seek and to answer for yourself, to your own satisfaction, the questions related to which approaches give you the best information related to the knowledge you seek to gain about nature. Then, to tell others what you've learned and why you believe your work to be useful to others, whether or not your results have confirmed your initial suspicions or taught you some surprising things along the way. 
I have never worried too much about doing things just as others do them routinely. Doing so would make a technologist out of this scientist. Try things out, modify your approaches to fit the need to satisfy your own curiosity, and celebrate the times when you learn something new and think that nobody has done that before.
Your "Why not ...?" makes me think that you may already know the answer to your own question! ;-)
I hope you often enjoy the feeling of success.
Sincerely, -Steve-
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Dear colleagues,
As far as I know, reverse saturation absorption is one of the mechanisms of optical limiting effect. Because when the light intensity is strong, the absorption coefficient increases, that is, light is absorbed more strongly by third order nonlinear optics material. So when we illuminate the material, initially when the input power increases, the output power behind the material also increases. At certain threshold, the output power is saturated. However, I'm not sure whether nonlinear refraction (nonlinear index n2) is the mechanism that causes the optical limiting or not. The nonlinear refraction only cause the beam to diverge or converge, only changing the light intensity without changing the power.
So, the issue is: Is the nonlinear refraction one of mechanism that causes the optical limiting effect?
I am looking forward to hearing from you.
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Hi Lam,
I had some experience with optical limiting (OL), and my comments about your question are: (i) nonlinear index (NI) could have important effect for OL if the material/structures have resonant features (micro-cavities, photonics crystal etc.) so that intensity at resonant mode(s) or wavelengths is changed with RI. Good design could make OL based on that. (ii) in general cases, OL effects are mostly from nonlinear absorption (NA) (saturable absorption, two photon absorption etc.). Note that, many optical nonlinear materials have both NA and NI. 
Hope that would help. By the way, I will visit HCM city on December, if you have time we can meet there. 
Best,
Dan
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Are their any papers to find the various response functions of Si(Li) detector below 10 keV photon energy?
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On the response function of solid state detectors, based on energetic electron transport processes, X-ray Spectrometry 32 (2003) 458-469
Is SQRT(N) a sufficient measure of the standard uncertainty in x-ray spectroscopy?,X-Ray Spectrom. 2017, 46, 367–373
Quality assurance challenges in x-ray emission based analyses, the advantage of digital signal processing; Invited review paper in Analytical Sciences 21 (2005) 737-745
An alternative approach to the response function of Si(Li) x-ray detectors based on XPS study of silicon and front contact materials, Nucl. Instr. and Meth. A 412 (1998) 109
The Effect of the Signal Processor on the Line Shape Advances in X-Ray Analysis, 53 (2011) 302
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I am studying a third order nonlinear optical organic material with a negative nonlinear refractive index, but the total refractive index is positive (n=n0+n2I, n2<0). These are natural materials. I now find that some researchers are studying on artificial materials with negative refractive index (n<0), which have unusual properties and can absorb waves of radar. Anyone can give me an simple idea about this Negative-index metamaterial and its fabrication as well as how it works.
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This is a long a deep subject.  The short answer is that it requires the material to have both a negative permittivity and negative permeability.  This is called a double-negative material.  There are ways to get a negative refractive in single-negative materials, but those are less studied.  Lots of physics is reversed in negative index materials.  First, it is left-handed instead of right-handed when looking at E, H, and the Poynting vector.  Doppler shift is reversed, Cerenkov radiation is reversed, and more.  
Watch the videos for Lectures 12 and 13 here:
Lots more could be said, but this is a start.
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Dear colleagues,
Recently, we have seen many studies on third order nonlinear optical effects and optical limitting in organic with CW laser. Some researchers wonder whether these effects are within the scope of the nonlinear optics or just thermal effects? Because, in these studies, wavelength of the laser is strongly absorbed by organic materials. And the self-focusing or self-defocusing effects occurs simply due to absorbing effect and heat is formed. Should we consider these effects as nonlinear optics effects? Any materials absorbing wavelength of the laser have self-defocusing effects. So are these effects is important? I think that these effects are nonlinear optics effecs because n2 depend on intensity and some materials absorbing wavelength of the laser don't have self-defocusing effects.
What is your point of view on this issue?
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Thank you for your positive comments, Prof.Raul Rangel-Rojo.
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Dear colleagues,
I have  read many  papers on Z-Scan measurements of material,  I see that the error is in the range of 25 to 40%. Some authors claim that the error is up to 50%. And the measurement of nonlinear index n2 by Z-scan and other methods are sometimes a difference of more than one order of magnitude. So which range the error of the Z-scan method lies in? And how many order of magnitude do results of measuring nonlinear index n2 by Z-scan method and other methods such as THG, EFISH, DFWM different?
I am looking forward to hearing from you.
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dear Lam
in my experience the main source of error in z-scan measurement is the uncertainty in the laser beam fluence measurements, or in other words in the beam shape. As a matter of fact the laser beam is often assumed to be a TEM 00 which is not always realistic. I think this fact can explain the reported differences in the published values and add large uncertainty in the results.
Following Rajeev Gandhi reply, I think it is worth to stress here that measurements using cw sources cannot be compared to pulsed ones since in the first case only the thermo-optical properties are probed. In  fact in this case the signal is originated by the thermo-optical coefficient dn/dT which is not a true third order nonlinear coefficient.
Finally, other techniques for third-order nonlinear characterization may probe other components of the chi^3 tensor, so that the measurements results may be not directly comparable to z-scan results.
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We are dealing with issues related to NEG pump dust being caught and lifted in the presence of a electrostatic field. Any info on q/m ratio of NEG dust will be much appreciated! 
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Solved!
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My group is working on several scientific instrument designs. In keeping with the open source ethos we would like to share them - but would prefer to put it the literature rather than using our website or one of the OSH repositories -none of which are quite appropriate. I have looked at PLOS One that has published some open source software tools (but not hardware yet) and at the Review of Scientific Instruments (that only does hard core new stuff - irrespective of price). They often publish tools with OS software as well. For our most innovative work they both would work - but I am also looking for locations to develop basic tool sets and add that to the literature so that we can all reduce our experimental research costs...the basic stuff we all need but currently pay enormous sums for - e.g. environmental chambers. Any good appropriate journals?
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The link given by Nicolas Guarin-Zapata is not working anymore.
But now there is the Journal of Open Hardware ;-)
"The international peer-reviewed Journal of Open Hardware publishes papers and reviews on technical, legal, economic, and sociocultural aspects of open hardware design, fabrication, and distribution. Its primary goal is to promote research and development of professional, academic, and community-based open hardware projects"
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I have a marine sediment sample that I have sieved at different mesh sizes. Can anybody suggest a method/ instrument to use to determine the density and the terminal falling velocity of the different sediment grain sizes? I am trying to determine the different density of different grain size sediment and the falling velocity over a water medium.
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A very simple method would be to put your samples in water, and watch the results:
For density: Archimedes principle (how much water does your sample displace/per weight)
For velocity: Pour your sample in a glass of water of a certain height and record the time it takes the grains to reach the bottom.(maybe use video for this)
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Hello, dear researchers, I have a modulation system which can give me the backscattered(reflection) and forward scattered (transmission) Stokes parameter of the particle under study. According to the Polarization Guide by Edward Collett, the Stokes of the elliptically polarized light  are given as:
S0=Ex0^2+Ey0^2
S1=Ex0^2-Ey0^2
S2=2Ex0*Ey0*Cos(delta)
S3=2Ex0*Ey0*Sin(delta)
where Ex0,Ey0 are the amplitude of the scattered orthogonally e.field components and delta is the optical retardation due to a material(the particle under study)
Absorption Stokes can be found out from Reflection and transmission light Stokes and from all three types of Stokes, we can find out the orthogonally e-filed components imaginary and real part and delta from S2 and S3 which is the angle between them.
now my question is that  with above-mentioned quantities can I find out the Scattering cross section? I used 400 nm to 700 nm wavelength.
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From wikipedia: "The cross section is an effective area that quantifies the essential likelihood of a scattering event when an incident beam strikes a target object, made of separate particles."
In other words,be careful when you define transmission as forward scattered light. I would rather say that light is either scattered, absorbed or transmitted. Extinction is defined as the sum of scattering and absorption,
Cext = Cabs + Csca,
in scattering cross sections. 
Also, the Stokes parameters describe the light, not scattering by the particle. You will have a set of Stokes parameters for your incident light, and a set of Stokes parameters for the scattered light. Note that the S0 is really the light intensity! I assume your modulation system describes the relation between the two sets of Stokes parameters i.e. the scattering by your particle (see Mueller Calculus).
Now, an easy way to find the scattering cross section would be to look at the intensities of the incident light and the scattered light:
Csca = Isca/Iinc
Just be sure to integrate the scattered intensity over all angles.
H.C. van de Hulst, Light Scattering by Small Particles, 1957.
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when selenium is alloyed with metals like In and Ag with varying levels there is a peak in the conductivity at a particular composition. Is there any theory other than Phillips and Thorpe model which may explain such type of behaviour?
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This type of behaviour is very common and observed in various properties but its explanation is not too unanimous....
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The equation for the electrons emitted is given in the attached file. I wish to approximate the given equation for a deutron beam of 300keV.
Ed=300keV.
I wish to plot the graph of N(E)=Number of Electrons vs Energy of Electrons keeping the average of emitted electrons  for 10-50eV? 
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It depends on the density of electrons. If it is more than a value that you can search it, you have to use Fermi Dirac distribution instead of Maxwell boltzmsn distribution function. 
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Can anyone explain why I am getting this error in SIMION when I try to adjust my FAST adjust voltage?
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Dear Mohammad,
Thanks for your reply.I already found the solution.I had to rename the file for new project!
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I am a PhD student from VNIT, Nagpur and I am working on rare earth containing glasses. I want suggestions for the calculation of Judd-Ofelt  parameters.
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The following (Judd-Ofelt Theory: Principles and Practices) I hope it helps you to solve your problem:
Judd-Ofelt Theory: Principles and Practices
1. Judd-Ofelt Theory: Principles and Practices Brian M. Walsh NASA Langley Research Center National Aeronautics and Erice, Italy (June 2005) Space Administration
2. Part I: Principles What is the Judd-Ofelt Theory? Based on static, free-ion and single configuration approximations: • static model - Central ion is affected by the surrounding host ions via a ‘static’ electric field. • free ion model - Host environment treated as a perturbation on the free ion Hamiltonian. • single configuration model - Interaction of electrons between configurations are neglected. The Judd-Ofelt theory describes the intensities of 4f electrons in solids and solutions. The remarkable success of this theory provides a sobering testament to simple approximations. National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
3. Distribution of Citations by Year 200 B.R. Judd, Phys. Rev. 127, 750 (1962). G.S. Ofelt, J. Chem. Phys. 37, 511 (1962). 150 ~ 2000 citations (1962-2004) Number of citations 100 50 0 62 72 82 92 02 Year National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
4. Referenced in 169 Journal Titles Top 20 Titles # of citations PHYSICAL REVIEW B 127 JOURNAL OF NON-CRYSTALLINE SOLIDS 108 JOURNAL OF APPLIED PHYSICS 90 JOURNAL OF CHEMICAL PHYSICS 83 JOURNAL OF ALLOYS AND COMPOUNDS 81 JOURNAL OF LUMINESCENCE 77 JOURNAL OF PHYSICS-CONDENSED MATTER 58 MOLECULAR PHYSICS 57 CHEMICAL PHYSICS LETTERS 48 OPTICAL MATERIALS 43 JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B 38 JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS 35 PHYSICA STATUS SOLIDI A-APPLIED RESEARCH 33 OPTIKA I SPEKTROSKOPIYA 30 IEEE JOURNAL OF QUANTUM ELECTRONICS 27 PHYSICS AND CHEMISTRY OF GLASSES 27 OPTICS COMMUNICATIONS 26 SPECTROCHIMICA ACTA PART A 26 INORGANIC CHEMISTRY 24 JOURNAL OF THE AMERICAN CERAMIC SOCIETY 19 National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
5. Prelude “Lanthanum has only one oxidation state, the +3 state. With few exceptions, this tells the whole boring story about the other 14 lanthanides.” G.C. Pimentel & R.D. Sprately, quot;Understanding Chemistryquot;, Holden-Day, 1971, p. 862 http://www.chem.ox.ac.uk/icl/heyes/LanthAct/I1.html ( some amusing mnemonics for the Lanthanides and Actinides) So much for ‘Understanding Chemistry’… Let’s do some physics! National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
6. Ions in Solids Solids • insulators (not semiconductors) • bandgaps are > 5ev (VUV photon) • produce a crystal field Ions • replace host ions substitutionally • transition metal and lanthanide series • unfilled electronic shells • Stark splitting from crystal field • optical transitions occur within bandgap Examples • Nd:Y3Al5O12 - Er:fiber - Cr:Al2O3 (Ruby) National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
7. Atomic Structure of Laser Ions National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
8. Atomic Interactions 4f 95d Hc >> Hso (LS-coupling) Hc << Hso (jj-coupling) Hc ≈ Hso (Intermediate coupling) !1 !2 !3 !4 5S 5I 4f10 5F 4 5I 5 5I 5I Configurations 6 Ho = central field 5I Terms 2S+1 L 7 (Electrons in field 5I Hc = Coulomb field 8 of the nucleus) (Mutual repulsion Levels 2S+1L J of electrons) Hso = spin orbit (Coupling between spin and orbital Stark Levels angular momentum) Vo = crystal field Ho >Hc , Hso >Vo (Electric field of host) Hund’s Rules*: F. Hund, Z. Phys. 33, 345 (1925) 1.) Lowest state has maximum 2S+1 2.) Of these, that with largest L will be lowest 3.) Shells < 1/2 full (smallest J is lowest), Shells > 1/2 full (largest J is lowest) *These rules apply only to the ground state, not to excited states. National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
9. Transitions and Selection Rules • Not all transitions between atomic states that are energetically feasible are quot;allowed”. • Forbidden transitions are “forbidden*” to first order, which means they may occur in practice, but with low probabilities. • Selection rules for transitions depend on type of transition – Electric dipole (E1) – Electric quadrupole (E2) – Magnetic dipole (M1) • Wavefunctions must have correct parity (Laporte’s rule) • Symmetry plays a role in selection rules – Vibronics, crystal field, other perturbing effects. * This nomenclature is historically embedded, although not entirely accurate. National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
10. Multipole Selection Rules ! ! Electric dipole operator (E1) P = quot;e! ri (odd operator) i ! equot; ! ! Magnetic dipole operator (M1) M =quot; ! I i + 2si 2mc i (even operator) ! ! ! ! 1 Q = $ ! k # ri quot;ri 2 i ( ) Quadrupole operator (E2) (even operator) S L J (No 0 ↔ 0) Parity Electric Dipole ΔS = 0 ΔL= 0, ±1 ΔJ = 0, ±1 opposite Magnetic dipole ΔS = 0 ΔL= 0 ΔJ = 0, ±1 same Electric quadrupole ΔS = 0 ΔL = 0, ±1, ±2 ΔJ = 0, ±1, ±2 opposite National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
11. A Brief History of Parity Otto Laporte (1902-1971) empirically discovered the law of parity conservation in physics. He divided states of the iron spectrum into two classes, even and odd, and found that no radiative transitions occurred between like states: O.Laporte, Z. Physik 23 135 (1924). Eugene Paul Wigner (1902-1995) explicitly formulated the law of parity conservation and showed that Laporte’s rule is a consequence of the invariance of systems under spatial reflection. E. P. Wigner, “Gruppentheorie und Ihre Anwendung auf die Quantenmechanik der Atomspektren”. Braunschweig:F. Vieweg und Sohn, 1931. English translation by J. J. Griffin. New York: Academic Press, 1959. Wavefunctions are classified as even (+1 parity) or odd (-1 parity). By convention, the parity of a photon is given by the radiation field involved: ED ( -1), MD (+1). For mathematical reasons, the parity of any system is the product of parities of the individual components. If the initial and final wavefunction have same parity (±1): ED: ±1 = (-1)(±1) Parity is NOT conserved. Transition is forbidden! MD: ±1 = (+1)(±1) Parity IS conserved. Transition is allowed! Laporte Rule: States with even parity can be connected by ED transitions only with states of odd parity, and odd states only with even ones. National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
12. Parity Selection Rules ED allowed ED forbidden MD forbidden MD allowed EQ forbidden EQ allowed s → p s → s p → d d → d d → f p → p f → g f → f s → f g → g p → g Orbital s p d f g Angular momentum ! 0 1 2 3 4 !- odd # electrons ! = ( quot;1)# i ! even odd even odd even !- even # electrons i odd even odd even odd National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
13. Historical Perspective I • J.H. Van Vleck - J. Phys. Chem. 41, 67-80 (1937) (The Puzzle of Rare-Earth Spectra in Solids) – Why are spectral lines in rare earths observable? – Electric dipole(E1), magnetic dipole(M1), quadrupole(E2)? – Concludes a combination is possible. – Suggests that crystal field makes mixed parity states (E1). • L.J.F. Broer, et al., - Physica XI, 231- 250 (1945) (On the Intensities and the multipole character in the spectra of the rare earth ions) – Considers all mechanisms. – Concludes quadrupole radiation is too weak. – Considers magnetic dipole , but as a special case only. – ED transitions dominate as suggested by Van Vleck! National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
14. Historical Perspective II • G. Racah - Phys. Rev. 76, 1352 (1949) (Theory of Complex Spectra IV) – Applies group theory to problems of complex spectra – Creates the tools required to make detailed spectroscopic calculations involving states of the 4f shell. – Revolutionizes the entire subject of rare earth spectroscopy. • Subsequent developments – Racah’s methods applied to crystal field theory. – Ideas of Racah applied to transition metal ions (Griffiths). – Practical calculations assisted by computer generated tables of angular momentum coupling coefficients. • By 1962 the stage was set for the next major development: The Judd-Ofelt theory of the intensities of RE transitions. National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
15. The Stage is Set “I suggest that the coincidence of discovery was indicative that the time was right for the solution of the problem.” Brian G. Wybourne “The fascination of rare earths - then, now and in the future” Journal of Alloys and Compounds 380, 96-100 (2004) National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
16. Judd and Ofelt Publish (1962) National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
17. States of an Ion in the Crystal The Crystal field, V, is considered as a first order perturbation that ‘admixes’ in higher energy opposite parity configurations: } quot;a V quot;# ! a = quot;a + % quot;# # Ea $ E# Mixed Parity quot;# V quot;b States ! b = quot;b + % quot;# # Eb $ E# ! ! ! ( +a V +* quot; + * P +b + a P + * + * V +b % quot; ,a P,b = !' + $ * quot; & Ea ) E * Eb ) E* quot; # φa and φb have the same parity (4f N states) φβ has opposite parity (4f N-15d states) V is the crystal field (treated as a perturbation) ! P is the electric dipole operator National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
18. Tensor Forms of Operators Racah defined irreducible tensors, C(k), which transform as spherical harmonics, having the components: quot; 4! % 1/2 Cq ) (k =$ # 2k + 1 ' Ykq & The position vector r is a tensor of rank 1, defined as r = rC (1) Dipole Operator Crystal Field ! ! Standard Form P = quot;e! ri V = ! ! Akq ri kYkq (quot; i , # i ) i i kq Dq = !equot; ri #Cq % D p ) = ! Atp ! rit quot;C p ) $ (1) (1) (t (t Tensor Form $ & i # % i i tp i Note: t is odd since only odd order terms contribute to parity mixing. Even order terms are responsible for energy level splitting. National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
19. J-O Theory Assumptions 1&2 1.) The states of φβ are completely degenerate in J. Assume an average energy for the excited configuration above the 4fN, that is, the 4f N-15d. 2.) The energy denominators are equal ( Ea-Eβ = Eb-Eβ ) Assume that the difference of average energies, ΔE(4f-5d), is the same as the difference between the average energy of the 4f N-15d and the energy of the initial and final states of the 4fN These assumptions are only moderately met, but offer a great simplification. Otherwise, the many fold sum of perturbation expansions is not suitable for numerical applications. National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
20. 4f and 4f N N-15d configurations 35 4fn configuration 30 4fn-15d1 configuration 25 Energy(×104cm-1) 20 Lanthanides in YLF: K. Ogasawara et al., 15 J. Solid State Chem. vol. 178, 412 (2005 10 5 0 Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb 58 59 60 61 62 63 64 65 66 67 68 69 70 Atomic Number & Symbol National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
21. Advantages of the Assumptions I.) Energy denominators can be removed from the summations II.) Closure can be used ( the excited configuration forms a complete orthonormal set of basis functions) #! quot; !quot; = 1 quot; III.) Angular parts of the electric dipole operator and crystal field Cq = ! C (1) !! U q (1) (1) and C p ) = ! C (t ) !! U p ) (t (t can be combined into an effective tensor operator %t 1 quot; ( + t 1 quot; . (quot; ) U U (1) (t ) = # (!1) 1+t + quot; +Q (2 quot; + 1) & )- 0 UQ ' ! ! !$ * , p q Q / q p quot;Q The 3j symbol ( ) is related to the coupling probability for two angular momenta. The 6j symbol { } is related to the coupling probability for three angular momenta. The Wigner 3-j and 6-j symbols are related to Clebsch-Gordon coupling coefficients. National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
22. Reduced Matrix Elements Nevertheless, combining the tensors for the electric dipole and crystal field terms in a combined tensor operator, UQ! ) , ( can be simplified further by the Wigner-Eckart Theorem: Geometry Physics (transformations) (Dynamics) % J quot; J# ( N f N! JM UQquot; ) f N! # J #M # = ($1)J $ M ' ( f ! J U ( quot; ) f N! # J # & $M Q M #* ) The matrix elements on the right side have been tabulated: “Spectroscopic Coefficients of the p N, d N, and f N Configurations,” C.W. Nielson and G.F. Koster, M.I.T Press, Cambridge, MA (1963). The 3-j and 6-j symbols have also been tabulated: “The 3-j and 6-j symbols,” M. Rotenberg, R, Bivens, N. Metropolis, J.K. Wooten Jr., Technology Press, M.I.T, Cambridge, MA (1959). National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
23. “Full Judd-Ofelt Theory” ! 1 * * J( $ () 1)J )M )Q (2* + 1)AtpY (t , * )' t $' J , a P , b = )e!! % %q Q quot;% quot; + a U ( * ) +b tp *Q & p quot;% ) M #& Q M (quot; # n! r nquot;!quot; nquot;!quot; r t n! &1 t ! ) Where, Y (t, ! ) = 2% ! C (1) !quot; !quot; C (t ) ! ' * n! Ea # E$ ( ! !quot; ! + This is the “Full Solution” of the Judd-Ofelt Theory. This form can be used to find electric dipole matrix elements between mixed parity states for individual Stark level to Stark level transitions. Application of “Full Judd-Ofelt Theory”: R.P. Leavitt and C.A. Morrison, “Crystal-field Analysis of triply Ionized lanthanum trifluoride. II. Intensity Calculations.” Journal Of Chemical Physics, 73, 749-757 (1980). National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
24. J-O Theory Assumptions 3&4 Oscillator strength (f-number) for electric dipole transition: 2 8+ mc 2 (n + 2% 2 ! ! 2 f = n& & 3n ## )JM P ) quot;J quot;M quot; 3quot;* (2 J + 1)e 2 ' $ L.J.F. Broer, et al., - Physica XI, 231- 250 (1945) 3.) Sum over Stark split J-levels (Assumes all Stark levels equally populated) $ J ! Jquot; ' $ J !quot; J quot; ' 1 *& Q M quot; ) & #M = + + Qquot; M quot; ) 2 ! + 1 !! quot; QQ quot; M = -J, -(J-1), …, 0, …, (J-1), J MM quot; % #M (% ( 4.) Sum over dipole orientations (Assumes optically isotropic situation) quot;1 ! t % quot;1 ! t) % 1 ($ q Q p' $ q Q = * * p) ' 2t + 1 tt ) pp ) Q = 0 (π-polarized, E ⊥ c) Q # &# & Q = ±1 (σ-polarized, E || c) National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
25. “Approximate Judd-Ofelt Theory” 2 2 8! mc 2 # n + 2& 2 Atp ) )) 2 (quot; ) f = n% (2 quot; + 1) Y (t, quot; ) * a U 2 *b 3hquot; (2J + 1) $ 3n ( ' quot; = 2, 4,6 p t =1, 3,5 (2t + 1) 2 Atp Defining Ωλ as: !quot; = (2 quot; + 1)# # (2t + 1)Y 2 (t, quot; ) Judd-Ofelt p t =1, 3,5 parameters 2 8! 2 mc # n2 + 2 & + 2 (quot; ) f = n% )quot; * a U *b Oscillator 3hquot; (2J + 1) $ 3n ( ' quot; = 2, 4,6 strength $ 2 (quot; ) SED = !quot; # a U #b is called the Linestrength. quot; = 2, 4,6 This is the “Approximate Solution” of the Judd-Ofelt theory. It can be used to find electric dipole matrix elements between mixed parity states for manifold to manifold transitions. National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
26. Judd-Ofelt Parameters In principle, the Judd-Ofelt parameters can be calculated “ab-initio” if the crystal structure is known, and hence, Atp: 2 Atp !quot; = (2 quot; + 1)# # Y 2 (t, quot; ) p t =1, 3,5 (2t + 1) n! r nquot;!quot; nquot;!quot; r t n! &1 t ! ) Y (t, ! ) = 2% ! C !quot; !quot; C ! ' (1) (t ) * n! Ea # E$ ( ! !quot; ! + # ! 1 !! & ! C (1) !! = (quot;1)! % ( 2! + 1)1/2 ( 2!! + 1)1/2 $0 0 0( ' # !! t ! & ! C (t ) !! = (quot;1)!! % ( 2!! + 1)1/2 ( 2! + 1)1/2 $ 0 0 0( ' 3-j and 6-j symbols can be calculated for ! = 3 (4f ) and !! = 2 (5d) Radial integrals between configurations and crystal field components, Atp, are difficult to calculate. Instead, Judd-Ofelt parameters are usually treated as phenomenological parameters, determined by fitting experimental linestrength data. National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
27. Intermission “The two papers of 1962 represent a paradigm that has dominated all further work on the intensities of rare earth transitions in solutions and solids up to the present time.” Brian G. Wybourne “The fascination of rare earths - then, now and in the future” Journal of Alloys and Compounds 380, 96-100 (2004). National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
28. Part II: Practices The Judd-Ofelt theory, in practice, is used to determine a set of phenomenological parameters, Ωλ (λ=2,4,6), by fitting the experimental absorption or emission measurements, in a least squares difference sum, with the Judd-Ofelt expression. Absorption Least Squares Judd-Ofelt Collect Matrix Measurements Fitting Parameters Elements # ( )=0 ! quot;2 Ωλ manifold ! (quot; )d quot; |<U(λ)>|2 !# k Transition τr and β Probabilities AJ′J The Judd-Ofelt parameters can then be used to calculate the transition probabilities, AJ′J, of all excited states. From these, the radiative lifetimes, τr, and branching ratios, β, are found. National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
29. Selection Rules Revisited ! j1 j2 j3 $ #1 t ! & ! j1 j2 j3 $ $ J ! Jquot; ' quot; %=0 $ ' #m =0 #! 1 !2 !3 & ! !quot; ! ( quot; 1 m2 m3 & % & #M % Q M quot;) ( % Unless: Unless: J! quot; J # $ ! = 2, 4, 6 ji ! 0 ji ! 0 t = 1, 3, 5, 7 !J quot; 6 !i ! 0 mi quot; ji ! quot;1+ t !L quot; 6 j1 quot; j2 # j3 # j1 + j2 m1 + m2 + m3 = 0 !S = 0 !! quot; ! # 1 ji , mi (1, 1/2 integer) ! 2 quot; ! 3 # j1 # ! 2 + ! 3 J = 0 : J # $ even Only d or g j1 # j2 quot; j3 quot; j1 + j2 ! 1 quot; ! 3 # j2 # ! 1 + ! 3 orbitals can J # = 0 : J $ even mix parity ! 1 quot; ! 2 # j3 New Selection Rules From Judd-Ofelt Theory S L J (No 0 ↔ 0) Parity Electric Dipole ΔS = 0 ΔL ≤ 6 ΔJ ≤ 6 opposite ΔJ = 2,4,6 (J or J′ = 0) Magnetic dipole ΔS = 0 ΔL = 0 ΔJ = 0, ±1 same Electric quadrupole ΔS = 0 ΔL = 0, ±1, ±2 ΔJ = 0, ±1, ±2 opposite National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
30. Judd-Ofelt Analysis I Matrix Forms 3ch(2J + 1) # 3 & 2 Sm = 8! e quot; 3 2 n% 2 $ n + 2( ' * manifold ) (quot; )d quot; S jm Components of 1 x N matrix 3 $ S = quot; M ij !i 2 (quot; ) SED = !quot; # a U #b t j quot; = 2, 4,6 i =1 N = number of tramsitions Mij - components of N x 3 matrix for square matrix elements of U ( 2 ), U ( 4 ), U (6 ) Ωi - components of 1 x 3 matrix for Judd-Ofelt parameters Ω 2, Ω 4, Ω 6 2 N % m 3 ( ! = $ ' S j quot; $ M ij #i * 2 LEAST SQUARES DIFFERENCE j =1 & i =1 ) ( ) = $2 ! quot;2 N & m 3 ) ( !(0) = M †M ) quot;1 !# k % ' M jk ( S j $ % M ij #i + = 0 MINIMIZED * M †Sm j =1 i =1 Judd-Ofelt Parameters 1 x 3 Matrix National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
31. Judd-Ofelt Fit (Ho:YLF) 6.0 Visible absorption spectrum of Ho:YLF 5.0 !ab (10-20 cm2) (! and quot; polarization) 4.0 3.0 2.0 1.0 0.0 280 330 380 430 480 530 580 630 680 Wavelength (nm) National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
32. Judd-Ofelt Analysis II With the Judd-Ofelt parameters, the ED transition probability for any excited state transition (J´→ J) can be calculated 64quot; 4 e2 * $ n2 + 2 ' 2 - Transition probability A J !J = 3 ,n & SED + n SMD / 2 3h(2 J ! + 1)# , % + 3 ) ( / . (Einstein A coefficient) 1 = # AJ quot;J Radiative lifetime !r J (natural decay time) AJ quot;J Branching ratio ! J quot;J = # AJ quot;J (fraction of total photon flux) J MD transitions are normally orders of magnitude smaller than ED transitions. Since ED transitions for ions in solids occur as a result of a perturbation, some MD transitions will make significant contributions. National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
33. Magnetic Dipole Contributions Magnetic dipole contributions can be easily calculated using an appropriate set of intermediate coupled wavefunctions for transitions obeying the selection rules ( ΔS = 0, ΔL= 0, ΔJ = 0, ±1). 2 ' quot; $ ! ! f n [SL]J L + 2S f n [S !L!]J ! 2 S MD =% quot; MD Linestrength & 2mc # 1/ 2 LS-coupled 2 - (J + 1) . (L . S ) * ! ! ! n '- ! 2 2 *$ f [SL]J L + 2 S f [S /L/]J / = &+(S + L + 1) . (J + 1) + matrix elements n 2 ((# !+ %, , 4(J + 1) )(! )quot; G.H. Shortley Phys. Rev. 57, 225 (1940) Intermediate coupled wavefunctions f n [SL]J = ! C ( S, L ) f n SLJ SL (linear combination of LS states) ! ! n quot; ! n f [SL]J L + 2S f [S quot;Lquot;]J quot; = n ! C (S , L )C (S , L ) f SLJ L + 2S f S quot;Lquot;J quot; n SL ,S quot;Lquot; Intermediate coupled matrix elements National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
34. Judd-Ofelt Results (Ho:YLF) National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
35. Testing the J-O theory Branching ratios can be measured directly from emission spectra. Use reciprocity of emission and absorption to indirectly “measure” the radiative lifetimes. Z! *$ hc ' - ! em ( quot; ) = ! ab ( quot; ) exp ,& EZL # ) kT / D.E. McCumber Zu +% quot;( . Phys. Rev. 136, A954 (1964). By comparing the measured emission cross section quot;5 3I& ( quot; ) ! (quot; ) = P. Moulton 8# cn 2 ($ r / % ) + ' 2I ! ( quot; ) + I # ( quot; ) ) quot; d quot; ( * J. Opt. Soc Am. B 3, 131 (1986). with the emission cross section derived from absorption, the quantity (τr/β) can be determined and the radiative lifetime extracted for comparison with the Judd-Ofelt theory National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
36. Reciprocity of Ho:YLF (5I7 ↔ 5I8) National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
37. Accuracy of J-O theory (Ho&Tm) Results are somewhat better in Ho3+ than Tm3+. Overall, the accuracy of the Judd-Ofelt theory is quite good, despite the approximations used. National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
38. Special Case I: Pr3+ ion (A failure of the standard Judd-Ofelt theory?) Pr3+ ions suffer from several problems in applying Judd-Ofelt theory 1.) Large deviations between calculations and experiment observations. 2.) Negative Ω2 sometimes obtained, in opposition with definition. 3.) Ω2, Ω4, Ω6 highly dependent on transitions used in fit. These inconsistencies are usually explained by the small energy gap (~ 50,000 cm -1) between the 4f N and 4f N-15d configurations in Pr3+ Solutions: 1.) Modify the standard theory: quot;!# = quot;# &1 + ( $Eij % 2E4 f ) ( E5d % E4 f ) ( ' 0 ) E.E. Dunina, et al., Sov. Phys. Solid State 32, 920 (1990). 2.) Remove 3H4 → 3P2 from the fit, or augment fit with fluorescence β’s R.S.Quimby, et al., J. Appl. Phys. 75, 613 (1994). 2 N +% ( . 3.) Use normalized least squares fitting procedure: ! = $ -' S jm quot; $ M ij #i * ! i 0 2 j =1 , & i ) / P. Goldner, et al., J. Appl. Phys. 79, 7972 (1996). National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
39. Special Case II: Eu3+ ions (Beyond the standard Judd-Ofelt theory)  The ED transitions 7F0 ↔ 5DJodd, 7FJodd ↔ 5D0 and 7F0 ↔ 5D0 in Eu3+ are “forbidden” in standard JO-theory. They violate the selection rules: • ΔS = 0 G.W. Burdick, J. Chem Phys. 91 (1989). • If J = 0 then J′ is even • If J′ = 0 then J is even M. Tanaka, Phys. Rev. B, 49, 16917 (1994). •0↔0 T. Kushida, Phys. Rev B, 65, 195118 (2002).  These transitions are primarily MD, but all three do occur as ED with low intensity in the spectra of some materials.  This implies that the standard Judd-Ofelt theory is incomplete. These ‘forbidden’ transitions provide an ideal testing ground for extensions to the standard theory.  What mechanism or mechanisms could be responsible? Are they meaningful! National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
40. Europium’s Peculiar Properties (Adventures of The Atom) The Atom, Issue 2 August 1962 (DC Comics) Coincident with the publications of Judd and Ofelt, who were both also interested in Europium’s peculiar properties. National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
41. Extensions I 1) J-mixing: The wavefunctions of the J ≠ 0 state are mixed into the J = 0 state by even parity terms of the crystal field. Explains the radiative transition 7F3 ↔ 5D0 in Eu3+. J.E. Lowther, J. Phys. C: Solid State Phys. 7, 4393 (1974). 2) Electron correlation: Electrostatic interaction between electrons is taken into account. Goes beyond the single configuration approximation and electron correlation within the 4f shell is incorporated by configuration interactions. Contributes to “allowing” the “forbidden” 0 ↔ 0 transitions such as 7F0 ↔ 5D0 in Eu3+. K. Jankowski, J. Phys B: At. Mol. Phys. 14, 3345 (1981). 3) Dynamic coupling: The mutual interaction of the lanthanide ion and the crystal environment are taken into account. Goes beyond the static coupling model. Explains hypersensitive transitions (transitions highly sensitive to changes in environment). M.F. Reid et al., J. Chem Phys. 79, 5735 (1983). National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
42. Extensions II 4) Wybourne-Downer mechanism: Involves spin-orbit interaction among states of the excited configurations, leading to an admixing of spin states into the 4f N configuration. This accounts for the observed spin “forbidden” transitions ΔS = 1 B.G. Wybourne, J. Chem. Phys. 48, 2596 (1968). M.C. Downer et al., J. Chem. Phys 89, 1787 (1988). 5) Relativistic contributions: Relativistic treatment of f → f transitions in crystal fields. Reformulation of crystal field and operators in relativistic terms. Importance unknown. L. Smentek, B.G. Wybourne, J. Phys. B: At. Mol. Opt, Phys. 33, 3647 (2000). L. Smentek, B.G. Wybourne, J. Phys. B: At. Mol. Opt, Phys. 34, 625 (2001). Review Articles Early development: R.D. Peacock, Structure and Bonding, vol. 22, 83-122 (1975). Later developments L. Smentek, Physics Reports, vol. 297, 155-237 (1998). National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
43. Summary Physical Mechanisms: (Not a complete list)  Crystal field influence based on static model. Second order in the perturbation. (This is the standard Judd-Ofelt theory).  Crystal field influence based on static and dynamic model. Second order.  Electron correlation based on static and dynamic model. Third order.  Spin-orbit interaction. Intermediate coupling and Third order effects.  Relativistic effects. Remaining Problems:  Estimating the relative importance of each mechanism is considerable. (Many competing mechanisms producing various effects. Entangled situation)  Ab-initio calculations still not entirely successful. - Theory of f - f transitions not yet complete. - Calculation of Radial integrals and knowledge of odd crystal field parameters. - Vibronics (Vibrational lattice-ion coupling)  Multitude of mechanisms and new parameters abandons simplicity. - Simple linear parametric fitting to observed spectra is lost. - Physically meaningful descriptions can be obscured. National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
44. What’s next? “It has been in a very real sense the first step in the journey to an understanding of the rare earths and their much heavier cousins, the actinides, but like many journeys into the unknown, the end is not in sight.” Brian G. Wybourne “The fascination of rare earths - then, now and in the future” Journal of Alloys and Compounds 380, 96-100 (2004). National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
45. Judd and Ofelt Finally Meet 40 years after publications B.R. Judd G.S. Ofelt B.G. Wybourne Ladek Zdroj,Poland - June 22, 2003 “4th International Workshop on Spectroscopy. Structure and Synthesis of Rare Earth Systems.” National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
46. 2007 School of Atomic and Molecular Spectroscopy 2007 will be the 45th anniversary of the simultaneous publications of Brian Judd and George Ofelt. A special session is certainly worth considering in the next course. “The fascination of the Rare Earths - 45th Anniversary of Judd-Ofelt theory” Possible invited lecturers: Brian R. Judd - The Johns Hopkins University, Baltimore, MD 21218, USA E-mail: juddbr@eta.pha.edu George S. Ofelt - 824 Saint Clement Road, Virginia Beach, VA 23455, USA E-mail: gsofelt@pilot,infi,net Lydia Smentek - Vanderbilt University, Box 1547, Station B. Nashville, TN 37235, USA E-mail: sementek1@aol.com G.W. Burdick - Andrews University, Berrien Springs, MI 49104, USA E-mail: gburdick@andrews.edu Francois Auzel -UMR7574, CNRS, 92195 Meudon Cedux, France E-mail: francois.auzel@wanaoo.fr Sverker Edvardsson, Mid Sweden University, S-851 70, Sundsvall, Sweden E-mail: Sverker.Edvardsson@mh.se National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
47. Acknowledgements Rino DiBartolo- Thank you for your years of wisdom and my first lecture on Judd-Ofelt theory in your office in ‘old’ Higgins Hall. Also for inviting me to Erice these last 10 years. Norm Barnes- Thank you for helping me see the laser side of life. The discussions we have had over the years remain with me. National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
48. Dedication Brian G. Wybourne (1935-2003) Professor Brian G Wybourne Commemorative Meeting: Symmetry, Spectroscopy and Schur Institute of Physics, Nicolaus Copernicus University, Torun, Poland June 12-14, 2005. A commemorative meeting in honor of Professor Brian G. Wybourne will be held in Torun, Poland from 12-th to 14-th June 2005. The aim is to celebrate Brian's academic life and his contributions to many aspects of physics and mathematics. This meeting will bring together friends, students, collaborators of Brian as well as people interested in the results and consequences of his research. National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
49. National Aeronautics and Erice, Italy (June 2005) Space Administration
50. National Aeronautics and International School of Atomic and Molecular Spectroscopy Space Administration Erice, Italy (June 2005)
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physics
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What Abdallah has said is absolutely right.
A standard example is the binding energy calculation of He4. It is made out of two protons and two neutrons. Masses are measured in atomic mass units where carbon is a reference point. One u is mass of carbon atom/12.
Mass of two protons is 2x1.00728=2.01456 u.
Mass of two neutrons is 2 x 1.00866=2.01732 u.
Mass of two electrons= 2 x 0.000549 = 0.001098 u.
total mass is 4.032978 u.
mass of the alpha particle is, 4.00153 u, that is the difference is 0.031448 u. Therefore the binding energy of alpha particle is 0.031448 x 931.5=29.29 MeV (approx). If you do not like to include masses of the electrons then the defect is 0.03035 u. This corresponds to a binding energy of 28.27 MeV (approx).
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When a spin possessing particle is in magnetic field B the spin 'rotates' around B. By example electron with spin on X will rotate perpendicular to B. But is this real? Can it be observed? Does this precession change the current in the coil creating B?
Secondly I tried to find out something about the classical situation. E.g. a compass must classically rotate then around B even when its blades are perpendicular to B.  But than I could not find anything. Also it will look like perpetum mobile. 
Thirdly I didn't see or can read about small magnets precessing around B? The spins must look like small magnets but there is nothing to confirm this?? And less about their effect on the B? Do really small magnet move precessingly around B and does this show up on the current of the coil?
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Dear dr. Ilian Peruhov,
about your first question, Robert Pohl (https://en.wikipedia.org/wiki/Robert_Pohl) devised a a working mechanical analogy between a sprinkler and spin transitions, which he included in the 1975 German edition of his book “Elektrizitätslehre”. I attach the pages I refer to. Abb. 14.14 shows the device on which the analogy is based. However, this mechanical analogy is not shown in every edition of Pohl's book.
While Larmor precession is a classical explanation of why matter shows a magnetic moment when in a magnetostatic field, NMR is a way of measuring the free induction decay (FID) response of diamagnetic substances (in solution). Whatever explanation is given for diamagnetism, the main problem when trying to visualize Larmor's precession of spin is that the spin itself is not a classically visualizable property. Thus, I would say that the directly observed quantity is the FID, indeed.
As for the directivity of magnetized needles, that remarkable property belongs to a small class of substances. The majority of matter is only slightly affected by magnetic fields, and one needs strong fields to observe tiny effects. Finally, you should keep in mind that, although NMR instruments have a spot where the field is homogeneous, generally strong magnetic fields are a bit non-homogeneous.
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I am doing research on tin and tin oxide nanoparticles using laser ablation method. Using Nd:YAG  laser in visible range (532nm) .By increasing the energy i have absorbed an increase in bandgap. What might be the reason.
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Dear  Jafary, nonlinear  grows of temperature with  pulse energy absorbance is main reason of your observation. The  phenomena has  been studied well. I provide You some conclusion from review paper:"Absorptivity as a function of temperature is an important consideration in practice and is usually modelled successfully as a linear function except around the melting point of the metal where there is a significant jump due to the sudden change of conduction electron density".
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Dear all,
for statistical reasons I would like to have a set of data from double slit experiment. Yet browsing the web I could not find anything. Does anyone of you know a website or ressource where one can download this set of data?
Thank you for your help.
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There's no difficulty in simulating the double slit diffraction pattern, to any precision, whether in the Fraunhofer approximation, the Kirchhoff formulation-in classical electrodynamics-or by solving the problem in quantum mechanics. And it's a standard lab experiment in wave optics.
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Suppose there are two Raman peaks and both of them show a shift with pressure. one of them after certain pressure start to come back to its original Raman peak position i.e. without pressure position. Please comment on this.
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In another approach, it might be mode softening of the particular mode with pressure. If this is the case how one can explain it. Please comment on this.
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Recent discovery of Gravitational waves is indeed exciting . It would be enlightening if the implications of this discovery is explained from different perspectives especially for the near future. Some possibilities could be , new insights into Planet perturbations, Climate change, Philosophies, new technologies of space/time travel etc.
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Hello, Narasim!
I'm not a physic but I also had a chilling feeling while listening to this news. The first thing I realized that this was the event that A. Einstein predicted about 100 years ago by theoretical background and, lastly, it was proved practically last week. For deep understanding, I dug up to some resources, mostly popular, and found my favorites:
The main prospective from it, in my point of view (that based on my survey), is an appearance of drastically new technique to investigate time and space and something else. Some compare it "to a deaf person suddenly gaining the ability to hear sound. An entirely new realm of information is now available.".
For me. the best striking strings about gravitational waves are the next:
"When asked to comment on LIGO's impact on the world beyond the scientific community, and about how gravitational-wave science might influence people's daily lives, Reitze simply said, "Who knows?"
"When Einstein predicted general relativity, who would have predicted that we'd use it every day when we use our cellphones?" he said. (General relativity provides an understanding how gravity influences the passing of time, and this information is necessary for GPS technology, which uses satellites that orbit further away from the gravitational pull of the Earth than people on the surface)."
Anyway, such a breakthrough gives all scientists much anticipations and hopes for their work (in any field of interests) and also is promoting science as the whole to a wide range of society. 
Best regards.
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What is main reason for the vacuum chamber in Electron Beam Melting?
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I agree with Gregory if "electron beam melting" means the technology of part manufacturing by selective electron beam melting of metal powder. In that case high vacuum is strictly recommended to avoid electron beam scattering and related electron beam defocusing effect. So you have to maintain vacuum to produce precise and high quality parts. But in some other technologies based on electron beam melting, zone refining for instance, different volumes are used for electron accelerator and production chamber, separated by the foil. Most commonly used material for the foil to extract electron beams of relatively low energy (200 kV or so) are aluminium and titanium - light metals with relatively long free-path length of electrons.
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by seeing naked eye can we think, what is the behavior of laser beam ?
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there is a very simple although less scientific method: Just take a business card and shake it along the beam in a dark room. If the laser is pulsed, you will see a line of dots, just because your pulse "ketches" the card in different locations. That works with rep-rates up to several kHz. For rep-rates faster, you will need a fast detector.
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laser plasma interaction
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In general every plasma can be inhomogenious and thus have spatial dependent refractive index fields (I was assuming a homogenious plasma, because if the plasma is inhomogenious the trivial answer is that you cannot do anything about focussing or defocussing as the electron density changes from point to point and hence also the refractive index - that can usually be not compensated by any power modulation of your beam).
Secondly not every nonlinearity does automatically lead to a refraction of your beam. Furthermore first you wrote that the beam has to have enough energy that the non linearities of the plasma come into play and then you claim that it is this non linearities, which (de)focus the laser beam - this is not really stringent.
The power and the timescale of the laser beam are also correlating, because due to energy conservation it holds that the shorter the beam temporally (at a given pulse energy) the higher is the power, you can deposit. However, non linearities come into play per definition at high amplitudes of your electromagnetic fields (the type of non linearity is hereby secondary).
So, you cannot say that you have just to go to higher laser powers in order to avoid self (de)focusing of your beam. Also the power density per unit area of the beam is proportional to the |E|² of your laser, which I also covered in my first post here.
So, in conclusion I want to emphasise again, the straight forward way to avoid optical effects in a plasma is to use a laser beam with small wavelength, low energy and a profile with maximum homogenity.
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We can specify up to two user definable emission spectra in silvaco. This is done by separately defining two spectra files apart from input deck. Can anyone tell me in which format I should define separate spectrum files and how to attach it to the input deck?
I am asking in context to user.spect or dope.spect as parameters of the material statement . Kindly refer to the LED simulator chapter in ATLAS manual for clear understanding of the question.
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you can consult the website of Silvaco, look where there are examples that can help you.
if you find such a thing, you can take the code section according to your needs (note the name of the file must be changed)
good luck 
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Which optically transparant material would combine a high refractive index (above 2 or so) with a very low Raman cross-section?
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Thanks! Of course diamond is not the most simple material to deposit or to pattern, so I continue to be on the lookout for other materials that can more easily be deposited as a smooth thin film.
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As a rule, BJT output characteristics are presented as a family of particular characteristics representing the function of the collector current IC of the collector-emitter voltage VCE while the base current IB is kept constant as a parameter. Maybe this two-dimensional way of presentation is widely used since it is convenient for printing on paper...
When we automatically measure and plot BJT output characteristics by a computer (even the primary Apple II), we have the unique chance to present them in a more attractive three-dimensional way. Now the collector current is a function of two variables - the collector-emitter voltage and the base current; IC = f(VCE, IB). The image on the screen is a surface, in which the particular characteristics IC = f(VCE) are represented by separate vertical sections of this surface.
I implemented this attractive experiment in the early 90's when I was trying to make vocational teachers in Bulgarian carry out real computer experiments in the semiconductor laboratory... but they proved unprepared for this... A program written on MLBASIC (an assembler extension of the embedded interpretator) was controlling an Apple computer equipped with an analog periphery - 4 DACs, 4 ADCs, power voltage-to-current and current-to-voltage converters (described, regretfully only in Bulgarian, in the attached link after the pictures below).
It is amazing that then I had no idea that I will reproduce this attractive experiment with my students whole 25 years later...  and really I will start doing it today... I made a "dress rehearsal" of the "show" at the university on Saturday evening. It was too late and dark in the laboratory... so movies I made were very poor (there was a mistake in the camera settings)...
(Measuring of a 3-dimensional transistor output characteristic by MICROLAB)
(Plotting a 3-dimensional transistor output characteristic on the screen)
(Temperature influence)
This question is closely related to the questions below:
It would be interesting for me to see what you think about this way of presentation. Is it the actual output transistor characteristic or only another attractive presentation?
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Dear Cyril,
Any representation has its objectives.
Let us analyse the two figures representing the same data. That is the transistor curves.
The transistor i-v characteristics can be expressed formally by the function:
IC= f( VCE , IB)
From the two port notation of the transistor, the output port parameters are IC and VCE.
IB represents  the  effect of the input port current on the collector current. 
Accordingly, to represent the output transistor characteristics on a two dimensional graph one has to choose VCE as a continuous variable and IB as a discrete variable having with proper steps. It is so that we sample the base current. This is the conventional way where the value of the base current is written on it as a label for the figure. Such transistor iv representation is used to solve graphically the tranistor circuit. We all know the concept of the load line and the DC operating point. so this presentation is characterized by its simplicity and ease of use.
Now it is to be compared by the three dimensional representation of the same transistor curves that you propose.
It is so that you add a third axes to represent the base current and then you have to draw the transistor curve at the new base current in an other plane shifted by the magnitude of the base current. So, there is no need to label the curve. This is the single benefit from the three dimensional representation. Which means that you use a different page to draw an i-v curve.
This new representation will complicate the concept of the graphical solution.
So, the only benefit is  not to label the i-v curves with the base current but with a more complicated solution.
I do not see any advantage from the three dimensional representation of the the output tranistor curves. In the opposite it brings unneeded complications.
This is my opinion on your proposal.
Best regard  
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We are working on induction heating and we are having trouble to measure the high frequency magnetic field strength (about 1 kA/m)? We have the coil design (nos. of turns and dia) and we know the current. From these quantities, we are using solenoid equation to theoretically estimate the magnetic field value.
But is there any instrument to measure the field directly at these high frequency. Normal gaussmeter is not working. Moreover, any metallic probe may get heated up extremely fast due to magnetic induction.  
Any help is well appreciated. Advanced thank you.
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Yes, a pick up coil is the way to go, attached to an oscilloscope.  To calibrate it, you can run an alternating current of known amplitude through a larger coil with a known diameter and number of turns, and then measure the voltage response in your pick up coil (which you would place inside the larger coil with axes parallel).  You can calculate the magnetic field produced by the large coil of known geometry and known alternating current.  Choose a few different alternating current values for the large coil and measure the resulting voltage in the pickup coil each time.  Then you can plot pick up coil voltage vs B field in large coil.  Now you have a calibration curve for the pick up coil.  Now you can measure an alternating  B-field of unknown amplitude.  Remember to orient the pick up coil to obtain the maximum voltage in the unknown field to get the full amplitude of the unknown field.  In summary you need a pick up coil, an oscilloscope with a bandwidth of at least 126 kHz, a source of alternating current, a way to measure the alternating current, and a large coil to generate a test field.  Good luck!
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Until recently, the Eotvos experiment (or the equivalence principle) has NEVER been validated under the strong magnetic field. And the strong magnetic field may be one possible factor to impact evidently the Eotvos experiment, resulting in the variation of gravitational mass.
On the other hand, it is necessary to validate the Eotvos experiment in the strong magnetic field. 1) When the distribution of strong magnetic field is uniform, the variation of magnetic flux density will alter the gravitational mass. 2) In case the distribution of strong magnetic field is non-uniform, the variation of magnetic flux density will result in not only the alteration of gravitational mass but also the emergence of strength gradient force.
As a result, the strong magnetic field must break the existing state of force equilibrium, transferring the existing equilibrium position of the neutral particle. Furthermore, on the basis of existing Eotvos experiments, it is feasible to validate the Eotvos experiment via applying strong magnetic fields in the experimental technique.
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I don't see what you mean by change of gravitational mass because of magnetic fields (at least not without utterly unobtainable magnetar like magnetic fields), but I can certainly see how even minute magnetisation effects in a strong magnetic field (by earth standards) could provide additional torques on a suspended test mass that would make Eotvos type experiments even more difficult than they are without a magnetic field. I would be interested to know how you think strong magnetic fields can validate the Eotvos experiment.
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I need experimental data for terminal velocity of  Hexene/Hexane/similar alkanes falling droplet in air to validate my numerical scheme. In brief, I want to know if there is any data for droplets with density ratio less than water droplet in air. can anyone introduce any related work?
thanks
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 When i know the phonon spectrum of one material, how can i get the potential interaction between atoms. (material is comprised of two different atoms). The phonon spectrum looks like the attached figure. any suggestion?
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The inter-atomic potential allows to calculate the dynamic matrix . From its diagonalization you can get the phonon dispersion. I think what you have to do is to model. You have to make assumptions whether there are only nearest neighbor interaction or next nearest neighbor interactions etc. Based on a model with free parameters (spring constants) you can try to reproduce the dispersion relation. This is similar to x-ray analysis where there is no straight forward possibility to solve the inverse problem. You need a model, and make a best fit with it. If the data are reproduced you get your force constants from the fit. If the data can't be reproduced you need to refine your model in your case by allow higher order interaction. 
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Currently we prepared CdO and SnO2 nano powder samples and we planned to measure the mechanical property of the powder samples. Can you give the available methods to measure the mechanical property of the powder samples?
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A flat tip nano indenter will help with indirect estimation of Young's modulus and has high reproduciblility, Also, most of the instruments come equipped with a PID controlled temperature chamber to measure temperature dependency of properties.
Further, if you have randomly shaped nano-particles I would personally suggest focused ion-beam etching to properly shape the contact area prior to measurements.
I hope it helps. 
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I am interested in the basic concept that might enable such a measurement.
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For example if we have a spin -1 system, then we know that its 3 components in a stern gerlach exptt will be +-1 and 0. Now I am interested in measuring S^2 for the same system, and I know it will have only two components +1 and 0. I hope its clear now.
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I want to form tungsten oxide thin film by dissolving tungsten powder in H2O2 but i can`t get complete solvation
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As a complement to above (clarifying) answer by V. Alejandro Suárez Toriello, I just want to add my two cents, by mentioning that WO3 dissolves in hot NH4OH (aq).
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We need to wind a pair of anti-Helmholtz coils and we would like to use wire that has a rectangular cross section to maximize the filling ratio.
Can anyone recommend a company that sells something usable (not to thick) and reasonably priced?
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You can browse the web site of phywe company, here you are
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I want to design an electron gun as electron source for a microwave tube using CST particle studio. Where we set the properties of particle source (electron in this case), the particle density is automatically taken by the code. However, i want to provide the actual electron current density but doesn't getting the option. Can anyone help in this ?
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while you define the properties of the Particle Source select "Fixed" in "Tracking Emission Model", then select "Edit" and define the properties of the Model. (CST Particle Studio 2011).
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10 nm gold particles are generally dissolved in PBS solution. in order to take SEM image of these particles, crystal lattices of buffer need to be removed. kindly provide some solutions.
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Try to centrifuge the colloid with 5000-6000 RPM for !5 mins. Pellet is formed. That can be used for SEM 
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When we shine a laser beam to the both side of the mirror (silver coated and uncoated), I am not getting fringes. How can we recognise both the surfaces? Is there any problem with my technique ?
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What about Brewster's Angle? The intensity of the light reflected in the dielectric surface should be =0 for p-polarized incident light.
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If you have any experience with this, I would like to know if this kind of ordinary, 1-channel waveform generator  (without any accessories like memory extensions and Time-base upgrades) is enough along with ordinary digital oscilloscope to carry out regular I-V and impulse-response measurements.
Right now I use generator and two multimeters for same purpose but we plan to do some upgrades. 
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The main issue here is the fact, that signal generator may not behave as expected, when you will connect it to a current source (which a solar cell is).  You may check thet in specification, or even better - send a query to Agilent tech support. In likely case that it cannot sink current opposite to driven voltage you will need to look for equipment  called source meter.  If you look for a bargain price, you may check
for genuine refurbished keithley equipment.
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Please see the images attached...
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If you plot the spectrum as a function of 1/wavelength, you may find that the peaks are more eqidistant with similar width.  Look at the équations describing interférence and you will see the dépendance on 1/wavelwngth. 
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if possible ,please suggest some paper or material.
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Thank you sir. i will follow these papers.
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We have two electrodes in a vacuum chamber and we applied a d.c. voltage . plasma formation is possible or not ? what will be the effect if we apply an a.c. voltage source ? what should be the minimum distance between the electrodes to form an plasma.
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Trying to put some order in the answers.
The answer depends on the value of the "vacuum" yo do consider.
- Poor vacuum = a small fraction of the atmospheric pressure. The applied voltage creates a real plasma made out of ions from the residual gas and electrons.
- UHV - Ultra High Vacuum = the value of vacuum in space, ~1 atom/m3. A plasma can be created from matter ripped off from the electrodes.
- The third answer is about the creation of particles in vacuum from vacuum. Ultra-high electric fields can create particles in vacuum but this takes place at the ultra-high energy levels one finds in stellar reactions. Sumit Mishra, this part is related to the high energies generated with ultra-short light pulses I wrote about in the answer to one of your other questions.
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what are their (femto, pico second pulses ) advantages over nano pulses.
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The conquest of knowledge has not limit, we must go everywhere we can go, explore every corner of the Universe.
I agree, this answer is too general. Here are some more practical arguments.
- If you want to picture a moving car with a camera you need to expose the film no more than about 1/100th of a second for the picture to be sharp. If you would like to picture the flying bullet of a firearm you would live the camera open in a dark room and shine the bullet with a nanosecond flash of light at the time it passes in front of the camera. When exploring the fastest dynamics of electrons in semiconductors you need femtosecond light pulses, and you want to explore the fastest dynamics of electrons because you want computer to run ever faster.
- This argument does not apply to attosecond light pulses because even the light objects like electrons do move too slowly at an attosecond time scale. The second strong argument favouring short pulses goes as follows. If you can put as much energy in an attosecond light pulse than in a nanosecond light pulse then the peak power of the attosecond pulse is a billion times larger than the peak power of the nanosecond pulse. When we will be able to produce pulses with peak powers larger than 1020 W/cm2 then we will be able to observe the interaction of two visible photons. In the mean time we will explore the field of photo induced nuclear reactions.
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I want to learn about different time zone laser ablation. what are the applications corresponds to these individually ? 
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Theoretical model of laser ablation (at least one of them) is called two temperature model. And it speaks separately about temperature (kinetic energy) of electrons and of nucleis. Basically it says the following: First electrons absorb the optical energy, and either in a ladder like manner (for longer pulses) or by direct multi-photon process (for shorter ones) are getting out of bound states to continuum.  Now two things can happen to the electron:
1. It will collide with a nuclei ant transfer its energy to phonons (thermalization)
After many collisions, nuclei will gain enough energy to escape the bulk
2. Electrons are gaining lots and lots of energy and leave the material (kind of multi-photon photoelectric effect). Nuclei stay cool. But after enough electrons have left, the nuclei remain unbound, and "fly away" due to room temperature energy.
The second mechanism, obviously affects much less area. In fact, being naturally multi-photon, the ablated area is proportional to intensity in the optical spot size in high power, effectively making the "hole" smaller. 
This second type of ablation is claimed to be used in medical devices for ophthalmology, where the size of the perforation is most critical. 
As far as I remember it was nice series of experiments shown by P. Bucksbaum at Stanford, using ultra-fast femtosecond ablation followed by ultra-short x-ray diffraction, where they have verified the second mechanism. I would check about years 2005-2009, but not sure exactly.  
Here is more recent paper, that looks relevant:
Optics Express, Vol. 20, Issue 28, pp. 29329-29337 (2012)
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is it possible to generate attosecond pulses by using femtosecond set-up ? can you give me an experimental idea about this technique ? 
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Hello Sumit (and others) --
(I posted this answer in the other thread before seeing you had created a new one. Here I have copied the answer for the benefit of anyone else following the conversation.)
People use several different kinds of lasers for producing the femtosecond pulse durations needed to drive high harmonic generation. This is actually its own field of research: in addition to ubiquitous Ti:sapphire-based systems, many researchers have achieved truly remarkable results relevant to attoscience with laser architectures based on optical parametric chirped-pulse amplification (OPCPA) or chirped-pulse amplification (CPA) in fibers and other solid-state gain media. Of course, each type of laser has its advantages (e.g. repetition rate, pulse energy, wavelength) that may make it more suitable for certain applications over others.
Speaking specifically of Ti:sapphire lasers (which you had asked about previously), most current setups used for generating isolated attosecond pulses involve a femtosecond oscillator, a pulse stretcher, the amplifier itself (which may consist of regenerative or multi-pass configurations, or both), and a pulse compressor. Because of gain-narrowing due to amplification of the pulse energy from the ~nJ to the ~mJ level, the pulse duration is usually limited to >25 fs, which is too long for generating isolated attosecond pulses with most common gating methods. (Because it relates to my own research, I will mention that an exception to this rule of thumb is double optical gating (along with its variants), which allows isolated attosecond pulse generation with pulses directly from the amplifier and compressor. This method can also work without facing the challenges of carrier-envelope phase (CEP) stabilization, which is required for most few-cycle gating methods like amplitude gating and ionization gating.)
Because of the long pulse durations after the compressor, most typical setups use a hollow-core fiber or filamentation tube to generate an ultrabroadband spectrum (e.g. several hundred nm) through self-phase modulation (SPM). This spectrum can be compressed using ultrabroadband chirped mirrors down to pulse durations as short as <5 fs. After this, the pulses are ready for gated high harmonic generation, which typically involves a focusing element, a gas jet or gas cell, and a way to separate the driving infrared (femtosecond) pulses from the resulting extreme ultraviolet (attosecond) pulses. The filtering and other specifics of the setup will depend on the type of gating that is chosen.
I hope this generally answers the question you had in mind.
Best,
~Eric (Institute for the Frontier of Attosecond Science and Technology, UCF)
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Is there a distinction of Sagnac effect between SRT and GR or absolute referential is enough? Are the clocks runing at same frequencies?
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Identical clocks have identical frequencies. The “twin phenomenon” (erroneously called a “paradox”) and its experimental verification in the Hafele-Keating experiment are explained by the fact that, according to Einstein’s relativity theories (SR and GR), the period of time elapsed between two events is dependent on the trajectory followed in getting from the first event to the second.
In the Sagnac effect two light beams emitted at the same time circulate in opposite directions and eventually collide. The two beams have traveled different distances when they collide simply because (due to the rotation of the whole experimental setup) the emitter at the initial time and the interferometer at the final encounter are not at the same place. So, obviously, a phase shift is to be expected. This has nothing to do with the details of relativity theories and has nothing to do with clock rates. It involves only the constancy of the speed of light.
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There are various methods available in the literature (Initial Rise, Peak Shape, Glow curve deconvolution etc.) which are used to analyse a thermoluminescence glow curve that recorded at a linear heating rate. But if the heating rate is not linear is there any method to accurately estimate the trapping parameters from the glow curve? 
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You are right that thermal quenching has to do with increasing temperature. The relation to heating rate is the following. Since an increase in the heating rate shifts the peak to higher temperature, at a higher heating rate the thermal quenching is in effect due to the higher temperature. Thus, at a higher heating rate, if thermal quenching takes place, the total area diminishes
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We expect a decrease or increase in the absorption of nano-collide under effect of magnetic field. 
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Dear Leonid
Thank you very much.
Best Regards
Ghaleb
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For a very simple and quick experiment, I need an Iron Single Crystal. I can return it because the experiment will be non destructive not only structural but only magnetic.
Because it is highly expensive, I do not have a budget and also there is no current project to buy it.
I need small (5-10mm) and oriented like [100], [110] and [111].
I appreciate your help.
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You can get the similar or apropriate answer by searching the keyword in the GOOGLE SCHOLAR page. Usually you will get the first paper similar to your keyword.
From my experience, this way will help you a lot. If you still have a problem, do not hasitate to let me know.
Kind regards, Dr ZOL BAHRI - Universiti Malaysia Perlis, MALAYSIA
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Atmospheric pressure, non-thermal plasma jets are  increasingly used in many processing applications, due to  their combination of inherent plasma stability and excellent  reaction chemistry, which is often enhanced downstream of
 the plasma source.
It is important to underline, that due to the high industrial demand for plasma
technologies and the resulting competition between system manufacturers, many of these manufacturers come to the market with closed box plasma systems (typically a plasma generator and its matching network in the single box), which
cannot be opened due to warranty issues. This leads to the situation where the only plasma diagnostic techniques available are optical techniques. Under these circumstances it is very challenging to develop an experimental approach, which would give a fundamental explanation of the impact of plasma physics on atomic physics, e.g., the role of metastable atoms, resonance energy levels, triplet and singlet energy scale, life time of electrons in an excited atom/molecular state, etc.
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This is quite a difficult task and is topic of current reseasch efforts.
First of all, it must be said that for a plasma jet propagating freely, without interaction with a substrate, there will be no "beam" of ions with a defined energy, but actually it will be better described by a distribution of energy. When a substrate is put in contact with the jet, an accelerating sheat may be formed, and the ion energy distribution function may be distorted. So the first thing one must have in mind in this case is that what should be measured is the ion energy distribution function (IEDF). It may happen to be sharp and peaked, but this is not always the case.
The second part to this answer is more practical: can I measure this IEDF? Yes, it is possible, and I know at least one method, but which have its drawbacks. The plasma jet may be put in contact with a very small sampling orifice, whose diameter should be not larger than 10 \mu m. The plasma particles are collected and then expanded trough some differential pumping stages, focused and accelerated into a energy analyzer in a UHV environment. In order to analyze only helium particles, one should place a mass filter after it. A SEM detector would suffice to count the particles. Many details and cautions must be taken when building such apparatus or even using commercial equipment, such as Hiden products. One of the main drawbacks of this apparatus is the fact that the sampling material interacts with the plasma, producing a sheath and distorting the IEDF. One may try to use a dielectric material similar to the substrate of the application of interest.
Any other idea or method to measure the plasma IEDF would be welcome and would surely give an important contribution to the field of plasma diagnostics.
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