Chemical Physics - Science topic

Polyamide 12 powder thermal conductivity varies with packing density and temperature, with inter-particle bonding being the primary factor influencing its performance in laser sintering. Temperature and time exposure are the most influential factors for deteriorating polyamide powder properties in the laser sintering process, affecting the quality of produced parts.

Laser sintering of polyamide 12 powder significantly impacts the microstructure and mechanical properties of sintered parts, with particle size distribution and crystallization temperature being key parameters in porosity formation. Using different ambient conditions and pretreatment can reduce the degradation of polyamide 12 powder in selective laser melting processes, resulting in better part properties. High-temperature flow properties of polyamide 12 powder deteriorate significantly, but agglomeration is excluded in the 100-140°C range, making it safe for laser sintering applications.

Please Find out more researches that might be useful:

· Heliyon, 9 (10) 2023: e21042 DOI: 10.1016/j.heliyon. 2023.e21042

· e-Polymers, 22(1) 2022:858-869 DOI: 10.1515/epoly-2022-0078

Best regards,

Hi,

it is called nanoreinforcement. Briefly, the polymer adsorbed on the particle surface gets immobilized. That, in turn, confines the movement of the neighboring polymers in the so-called frustrated layer. Less mobility = less deformation -> the material is stiffer. This effect is especially strong above Tg, where polymers have high mobility, but it could also be detected below Tg.

The interaction is rather short-ranged (<100 nm), so you usually need a large surface area of the nanofillers to see the difference. Therefore, you must always consider the filler dispersion.

Nanoparticles usually have different properties to polymers, and you would choose them according to the application. For instance, metal particles or carbon nanotubes for increasing electric conductivity, nanodiamonds for increasing heat conductivity, ferrite particles for introducing magnetic properties, etc. Some other ideas might be found here:

Dear Professor,

Dr. Nishant

Thank you for your answer and adequate clarification, and I am pleased to cooperate with you in any future project or research.

Dr. Yousra Amer

If you don't want to make it open access, are there any indicators why that shouldn't be possible?

Interesting questions Romar, I think that first of all, it is important to note that the two methods of biomass activation you mentioned each has merits and demerits. Several factors need to be considered in the choice of a surfactant or activation reagent. It is also important to note that, different activation reagents have different effects on the biomass. It is widely argued for example, that oxygenated compounds have a good activation effect on biomass. However, as I have indicated earlier, the output of the activated carbon is largely dependent on so many factors, including the chemical properties of the biomass. I have used surfactants such as H2SO4, H3PO4, KOH, HNO3, KCl, Na2CO3 etc. What I observed with KOH for example was that, there was high biomass loss in the process due to cell wall disruptions and the efficiency of the modified biomass was also low. H2SO4, H3PO4 and Na2CO3, KCl had a good activation effect on the biomass. One way to detect if new functional groups emerged on surfaces of the AC or not, is to do an FT-IR analysis on the unactivated samples and compare them with the AC among other evaluation tests. In summary, some biomaterials give good performance if they are physically activated or modified, some other materials give good results via chemical modification and some require hybrid. Hope my input is helpful. Cheers Henrik Romar

Hello .. Good idea .. Please take advantage of this research ... Good luck@

check this out

Thanks for the multiple replies.

The probability of pick-off annihilation in positronium (Ps) is primarily due to electron density, as Rüdiger Mitdank has pointed out. It is described by the overlap of the positron and electron wave functions. However, in practical terms, it is not determined by that alone, but is also affected by various environmental factors. In this discussion, I would like to get into these factors.

For example, water and many other liquids expand as their temperature rises. Since expansion decreases the molecular density (electron density), it is assumed that the higher the temperature, the longer the Ps lifetime. However, this assumption is not true. In fact, the lifetime of Ps is shorter in warm water than in cold water.

Similarly, the relationship between Ps lifetime and pH is not easy to estimate. Therefore, we should base our decisions on experimental data.

Most of the basic Ps chemistry was done in the 1960s and 1970s. In those days, the resolution and stability of measuring instruments were not as good as they are today, and the use of computers was limited. Straight lines were drawn with a ruler on hand-drawn one-log graphs. Therefore, the environmental factors that were reported to be "independent" at that time may or may not be due to the lack of measurement accuracy. As the application of positron science to medicine has progressed, motivation to revisit some of the issues has arisen.

I hope somebody will continue to let us know if you have any information on the relationship between pH and the lifetime of Ps. Thank you very much for your time.

It is a disadvantage of the sterilization method that ethylene oxide sterilization remains only residue rather than the physicochemical effect on rubber materials. You can do a literature search on this subject with google academic.

Several software programs are available to study the physical and chemical properties of materials. each software is implemented in a method. for example the Win2k it is implemented in the FP-LAPW method ..

Dear Cory Camasta, Three degrees of freedom come from free motion, one from rotational and one from vibrational & E= 5/2 K_BT. The remaining rotational degree has a very small moment of inertia as some participants noted previously.

See the following external post for the full explanation regarding the separation of levels mentioned by Prof. :

https://physics.stackexchange.com/questions/168943/in-counting-degrees-of-freedom-of-a-linear-molecule-why-is-rotation-about-the-a

Yes, archeology is an interdisciplinary science, because both in the research methods used in excavations and when analyzing artifacts found in excavations, exhibits, etc. often originating from distant, old eras, constantly improved research instruments are used, perfected using modern technologies created and developed in various fields of knowledge, in various disciplines of science and also the results of research, scientific discoveries provide knowledge about the history of the development of civilization, man, specific old cultures, determinants of technology development, factors of development of human creativity, development of art, trends and trends in art, development of human relations in relation to nature, etc. Archaeological discoveries provide source knowledge for the development of many other fields of knowledge, update and enrich historical knowledge on almost all aspects of human activity in more than Sci., Currently, research methods and techniques in the field of archeology are being improved through the use of ICT, Internet and Industry 4.0 information technologies. Thanks to the implementation of these modern technologies for archaeological research and the use of their results, sharing archaeological knowledge databases in the open formula, online knowledge databases, the possibilities of using archeological research results also in other science disciplines are increasing.

Greetings,

Dariusz Prokopowicz

Simply go back to the definition of Hartree-Fock. The idea is to approximate the many-body wave function with a single Slater determinant. Because of the determinant, any non-orthogonal component of the orbitals is irrelevant and only the orthogonal part survives. In other words, if you take a non-orthogonal set of orbitals and construct a Slater determinant out of those, you will get the same determinant if you would have first orthogonalised them (Gram-Schmidt, Löwdin, canonical, etc.). You still have the same volume.

Generally one prefers to work with orthogonal orbitals, since this makes it easier to work out the expectation values of the determinants (e.g. energy) via the Slater-Condon rules. Generalisations also exist for non-orthogonal orbitals, but due to the cross-terms, you get overlap matrices, cofactors and adjugates all over the place. So in this sense, orthonormal orbitals are more a convenience than a necessity. Non-orthogonal orbitals would not add anything (the determinant remains the same).

On the other hand, once you have used the Slater-Condon rules to work out the expectation value of the Hamiltonian, this energy expression is only valid for orthonormal orbitals. So you better enforce orthonormality in the optimisation, to get a physically sensible answer out. (All orbitals could become identical, so all the particles would occupy the same state. So you would get bosons out instead of fermions.)

- First, let's review some basic equation:

+ From VASP source code:

CDER(k, m, n, j) = <u_m|- i d/dk_j | u_n> = - <u_m| r_j |u_n> (j = x, y, z)

(k=wave vector; m, n are band indices, u is periodic part of the wave function; for now, I ignored spin index of CDER)

CDER can be obtained from WAVEDER or WAVEDERF using this function: https://github.com/hungpham2017/mcu/blob/master/mcu/vasp/utils.py#L82

+ The square of CDER is defined as the dipole transition matrix:

dipole transition matrix (k) = CDER(k, conduction_index, valence_index)^2

+ Finally the transition probability R per unit cell is given by:

R = pre-factor * sum_k (dipole transition matrix (k) )

or R(k) ~ CDER(k, conduction_index, valence_index)^2

To know the value of pre-factor, please see the section 6.2.2 of this book:https://www.springer.com/gp/book/9783642007095

If you are not interested in the absolute value of R(k) with the correct unit, then you just need to plot the R(k) ~ CDER(k, conduction_index, valence_index)^2 as a function of k.

- In practice, the function I wrote will read the WAVEDERF file and give you:

CDER(spin, k, m, n, j). Simply, do the math:

R(k) ~ CDER[spin, k, m, n, 0]**2 + CDER[spin, k, m, n, 1]**2 + CDER[spin, k, m, n,2]**2 with m, n are indices of conduction and valence band.

I will include this R(k) calculations (with correct unit) in my code soon.

Hope this is helpful

Dear Samvit Menon, you can get the Trees parameter from the best fit of your observed tfansitions, using a ligand field program. Best suited for this is the program AOMX, developed by Heribert Adamsky and co-workers. If you are intersted we can supply you with the program.

Yes, there are articles about this and though authors categorise some effects as "good" or "bad", I honestly think it depends on each niche the floating PVs are installed.

It is known that floating PVs produce more energy than land ones because of water reflection. As to the effects cause on the water itself:

- The shading created by the panel prevents growth of algae (which, again, can be good or bad depending on the approach);

- Prevents excessive water evaporation, thus it can be used as a tool in arid and semi arid spaces;

- Inhibits the convertion of bromide into bromate;

Here's an article for you:

Hello Ahmed Abd Burghal

Types of biosensors :

More details here : https://www.elprocus.com/what-is-a-biosensor-types-of-biosensors-and-applications/

Best regards,

Marie B.

As you might observe from the earthworm dissection after the reproductive glands the calciferous glands are a major investment of earthworms.

Earthworms depend on adequate calcium for the digestive process and in addition the diagnosis of a well wormed soil is by the presence of excreted calcitic limestone granules.

The majority of earthworms are inhibited and do not do well in acid soils. soils with little organic matter, and dry soils.

The addition of lime and manure can supercharge the soil by the enrichment of the soil in earthworm castings.

If farmers can provide lime animal manure and water the worms can act as bio tillers.

A single earthworm can produce 5 kilograms of castings in a single year.

In a grass legume pasture with manure addition millions of earthworms can be produced in a single hectare.

Earthworm castings are also 30% carbon it might be possible that the resolution of global warming is global worming and that would need liming and maintaining the earthworm habitat to optimize their amazing abilities.

While the human of 76 kg resides in a hectare the mass of earthworms can reach 1000's of kgs per hectare more than any other life forms in the living soil.

Google (and Wikipedia) is your friend:

Bhanwa,

maybe my little attache scribbling helps a bit.

Very difficult but interesting question indeed. One of the ways could be to look into experimental results of the modern day reefal growth in the near by areas and compare it with the ancient carbonate buildups. The temperature and physico-chemical conditions of the modern day sea water, calcium content, co2 content and transgressions and regression in the past need to be compared as all of these factors would have also influenced reefal growth in the past. I am sure it would be interesting study. The satellite images would also help but how far, these may not be available for distant past so analogues need to be developed to estimate various aspects. Regards

The starting point of thermodynamic logic is: 1) opposing perpetual motion. 2) The irreversibility of dynamics. Let's look at how to get Carnot efficiency = 1-T1/T2.

1.1 There are many kinds of type 2 perpetual motors, each of which is a natural phenomenon.

A) Machine A: against the irreversibility of thermodynamics (diffusion, heat conduction, friction, etc) - dynamics;

B) Machine B: Utilizing the Difference of Carnot Efficiency (Reversible Thermodynamics) - Thermodynamics

1.2 A and B belong to different disciplines. There is a parallel relationship between them and there is no logical mutual inevitability.

1.3. Logic of the Second Law of Thermodynamics:

Experience induction, deny that A machine==> B machine can not be manufactured==> All material Kano efficiency: 1-T1/T2.

1.4 The logic of the second law of thermodynamics violates the physical logic that A and B cannot be inferred from each other.

1.5 The second law of thermodynamics elevates the "irreversibility", which is in fact only a kinetic experience.

📷 Detailed discussion can be found in the following figure.

The color is due to your nanoparticles. So it will independent on the methods.

You can refer to The United States Pharmacopeia (USP) or British Pharmacopoeia for reference.

There is other book called Remington practice of pharmacy can also partially solve the issue.

The best option would be the drug information provided in the USFDA Accessdata site or EMC Summary of product characteristics and PubChem site as the information provided here are supposed to be most accurate legally for any particular molecule.

Hello Abdelwahab

Try looking at nist webbook

It has chemical and physical property data of almost all compounds

Good Luck !

Physical adsorption (characteristic of weak van der Waals forces) and Chemical adsorption (characteristic of covalent bonding). Physical adsorption is very effective and occurs usually at a temperature close to the critical temperature of a given gas. Chemical adsorption occurs usually at temperatures much higher than the critical temperature.

Of course, yes. To give an example, from quantum chemistry, let z be a perturbation parameter and suppose that we computed E(z) function by using Rayleigh-Schrödinger perturbation series (n>3 order). This function involves singularity points in the complex z plane which are responsible for the convergence of the perturbation series. In terms of Schrödinger equation (and conformal mapping) these singularities manifests some changes in molecular geometry or in basis set. Such points may connect the ground state to an excited state of the molecule (generally to a low lying excited state or the one as its lowest symmetry). Some other points behave as critical points upon dissociation. MP4 and CCSD(T) type computations reveal such phenomena.

Hi Enmanuel Duarte, the ODE solver will return a solution set of data points from the universe of discourse. So I think, at most, you can only get the 3-D line plot, not the surface, unless you want to obtain the slope field.

yes

Mr. Koyal,

The topic of your question is basic knowledge module Inorganic Chemistry I.

What is the effect of harvest time of mushrooms on physical, mechanical and chemical properties ?

To start with, I shall give a good site that provides information about the preparation & properties of M/F resins. On the left side of the page, you can see reference to U/F resins:

Best wishes for success in your research.

hi,

A simplest approach would be to test thermal conductivity of a fluid under use which is as per your need/choice and compare it with the thermal conductivity of the same fluid after adding the appropriate metal/alloy nanoparticles. Usually the addition of such metal nanoparticles enhances the thermal conductivity of the fluid.Easy said than done. You need to optimized on many levels. An arbitrary choice for fluid and type of nanoparticle may give erratic results or may even cause degradation of the device under study. Just make sure you do the thorough research before you actually start mixing things together.

Regards

Dear samiee

I agree with Dr. Miri and also tissue culture techniques that ensure genetic stability are particularly useful for in vitro mutation induction and mutant plant regeneration. In vitro method needs lower concentration of chemical agents that could be safer incomparision of in vivo.

Best wishes

Hi Sk Imadul, Thanks but i need more viscous solvents at least > 30 cP

Yes you can say it. But in nano-hybrid, the physical property of the individual does not remain intact. Rather, new properties generate.

Nanocomposites are nanomaterials that incorporate nano-sized particles into a matrix of standard material. The result of the addition of NPs is a drastic improvement in properties that can include mechanical strength, toughness and electrical or thermal conductivity. The effectiveness of the NPs is such that the amount of material added is normally only between 0.5 and 5% by weight.

There is no ambiguity in saying this that all of the components within the Nanocomposites exhibits strong molecular interactions. For better understandings i suggest you to study the following.

In above link you would see that how we have developed the nanocomposites of Amorphous and Crystalline Nano-materials.

Mr. Al-Mobarak,

It is modified chemically.

Physical modification means thermonuclear rection.

sure sir.... thank you. Please find the files attached

Wow. Thank you a lot. The link is very useful. Apart from control measure, I too have my concern of the situation on standing paddy crop.

The original CAM-B3LYP with ω = 0.33, α = 0.19 ,and β = 0.46 would have the following Iop values in a gaussian input file (of course the IOp provide redundant information in this case):

# CAM-B3LYP/basis iop(3/107=0330000000) iop(3/108= 0330000000) iop(3/119=0460000000) iop(3/120=0460000000) iop(3/130=01900) iop(3/131=01900)

An input for a modified version of CAM-B3LYP with ω = 0.30, α = 0.25 ,and β = 0.40 would be

# CAM-B3LYP/basis iop(3/107=0300000000) iop(3/108=0300000000) iop(3/119=0400000000) iop(3/120=0400000000) iop(3/130=02500) iop(3/131=02500)

Dear Dino Rimantho

Dynamic system is relation between stimulus and responds. If we know characteristic of the system we can predict the respond, especially related with the stability of the system, stability or chaotic responds. Really if we give input reference to the system we expected the result is the same as input references, if the result is different it is mean the system has a failure. Using risk management method using ISO 31000 or ISO 14971 we can analyze failure mode of your system, effect of this failure (level of severity) , probability of this failure and how to detect.

Salam

Susanto

Interface is the two dimensional BOUNDARY between two surfaces.  Interphase is the three dimensional REGION between two phases.  Thus, we talk of the interfacial adhesion in a fiber-matrix composite being determined by the strength of the interaction between the fiber and the matrix at the interphase. There is an intrinsic problem with this definition that has to do with length scale.  What appears as an interface at large length scales (mm) may look like an interphase at smaller length scales (nm).  I think, it is for this reason, the word interphase is not that widely used in materials science, unless interphase, an intermediate phase, is being explicitly discussed.

Hi, William. 

I don't understand your mean by "..., that should have been a give away indicator". please give more explanation. Notably, as I said previously, the balloon was such one that remained air-inflated for several days after the entirely fade of the water.

Regards  

Dear Alejandro Martinez,

I actually thank you very much for your help. I've tried many times your method and I found it successful. so thank you. but when I was writing the key words, I didn't add "set bace".

besides, would you tell me were you get those informations? I want now to understand the meaning of these words.

best regards

Dear Aslamic,

The enclosed article can help you. good luck in your project.

I read about the moisture effect in its MSDS. I tried to make the solid films in open environment at around 25-28^oC , it took around 40 hours to make a brittle film 

You are doing nothing wrong. At x->0 your equation gives ln P  = -∞ from which we obtain P = 0.

Lower Z phosphors are suitable for any human or environmental dosimetry as they exhibit less over-response whereas phosphors having Z around 15 exhibit huge over response, which need to be corrected via thick metal filters so as to make their response to photons flat. Generally TL and OSL phosphors having Z greater than 15 are rarely used in dosimetry but Film badge based on AgBr having Z ~40 is popularly used. SO high Z may be used. Similarly BaSO4 is used in imaging plates etc. but possibly not in radiation dosimetry. If Z  of phosphor is 7-8, it is used in medical, personnel dosimetry etc whereas phosphors having Z 15 are less popular in medical dosimetry but used in personnel monitoring like CaSO4: Dy being used in India  but not recommended for radiotherapy or patient dosimetry where LiF based are preferred.  

So

(Zeff=7.4 - 10), personnel as well as medical (?)dosimetry

(Zeff=10 - 15)? personnel monitoring only

>15 not for personnel as well as medical but other applications where human body dose is not evaluated etc. can be used

Usually the cutoff is set to 2.5xSigma or less than half of the simulation box length. A good book to start with is by Frenkel and Smit.

1. Biological control using PGRB/F such as bacillus and mycorrhizal antagonists

2. Drenching using copper and sulphur based fungicides

3. Cultural practices such as roguing diseased plants, solarization and non-host plant cropping

4. Using biofumogants

There are likely many labs where this occurs. Run a google scholar search of "unconverted PL" if you need sub-ps resolution. If ps resolution is good enough, a Streak camera may suffice. You may also look into studies of 2D Transition metal dichalcogenides or other material systems where the PL lifetime are quite short. That should give you an idea of the groups that are active.

SDBS seems effectively to be sodium dodecyl benzene sulfonate, so Saeed is correct in writing a possible H-bond between the sulfonate anion and the acidic H. This interaction is only possible with the unionized RCOOH, for example in the solid state or in some organic solvent which cannot compete for H-bonding (I may discuss this point further if necessary). The H-bond is seen as "a non-covalent bond". "Chemical bonding" is not well defined in this context, but a covalent bond is unlikely between these two molecules.

Dear Dr. Islam (Aminul),

Dr. F. N. Ponnamperuma*, the celebrated Rice Soil Chemist and former Principal Soil Chemist, International Rice Research Institute (IRRI), Los Banos, Philippines listed the following following chemical characteristics of fertile wetland rice soils:

pH 5.0-6.5, ECe (mS/cm) <2, Eh (after submergence, in volt) +0.2 to -0.2, org matter (%) 2.0-3.5, total N (%) >0.2, total P (%) >0.02, Olsen P (mg/kg) >10, exch K (mmol/kg) >2, avail S (mg/kg) >10, CEC (mmol/kg) >200, clay composition >50% montmorillonite, active Fe (%) >0.5%, active Mn (%) >0.05, avail Zn (mg/kg) >1, avail B (mg/kg) <5.

(*I was privileged to conduct my Ph.D. thesis research under the guidance of Dr. F. N. Ponnamperuma at IRRI, Los Banos, Philippines during early 1980s).

Ref: Ponnamperuma FN (1981) Properties of Tropical Rice Soils. Text of a Series of Lectures Delivery to Graduate Students at the Topical Agriculture College, H. Cardenas, Tabasco, Mexico on 23-25 July 1981.

Hope you find this input useful. 

Up-vote on the response of Aras Kartouzian.

To elaborate, it sounds like you are interested in the magic clusters. Magic clusters are clusters of atoms consisting of some integer number of complete shells of atoms about a single central atom. Suppose you take a single atom and surround it with exactly one layer of atoms in a close-packed arrangement. It takes exactly 12 balls to completely surround a central ball (Try it with tennis balls, if you can find enough tennis balls.) This is smallest magic cluster. It has one central atom and 12 surface atoms for a total of 13.  If we add a second shell of atoms, it takes 42 atoms to complete the second layer. This cluster has 55 atoms total, 13 in the interior and 42 on the surface. It takes 92 atoms to make a third shell. This cluster has a total of 147 atoms. The next cluster has 309 atoms. The sequence is: 1, 13, 55, 147, 309... These are the "centered icosahedral numbers".

Dear Jayesh

Interesting to your question I want to ask the result of last year experiments as "impregnation in H3PO4 (85% solution) at 550°C or in molten KOH at 800°C" or "gasification in a stream of water vapour at 850°C, or of CO2 at 900°C".

If it is possible say what happened.

Thanks a lot

Dear Dr.Monajjemi

i had a calculation using MRCI method. i will send the input and output files to you by email. please have a look at it and give your comments on it. 

thank you 

Yes, I had calculated it using Gaussian, considering an isolated molecule.  But, wanted to obtain an answer considering many molecules (making a system) and then find out.

No. RDFs are normally for solutions. I am suggesting you to read some sample articles that have used molecular dynamics or Monte Carlo simulations for similar compounds to yours in order to have an estimation about the required number of molecules and methods of calculations with reliable results.

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)

Dear Daniel,

All bonding orbitals have negative energies, while all antibonding orbitals have positive energies. This is because the zero of energy is defined as a non-bonded state: bonding orbitals are more stable (lower energy than zero), while anti-bonding orbitals are less stable (higher energy than zero). Most non-bonding orbitals are at or close to zero in energy.

Your results indicate that the HOMO is more stable than the LUMO and the gap has a positive value, which is fine.

Regarding the negative value of the LUMO: I have seen negative LUMO values when calculated in certain methods, but other methods give positive values. It depends on the calculations method you use. It is suggested that you rerun your calculations using both time-independent and time-dependent DFT (TD-DFT). The DFT functionals may include the local spin density approximation (LSDA), (GGA) functionals, hybrid GGA functionals, hybrid meta GGA functional.

Hoping this will be helpful,

Rafik

Mr. Tikendra varma

Sterilize by autoclaving, as first step seperate fungal mycelium by centrifugation. Then wash the pellet or mycelial mass thrice with double distiilled water (if required centrifuge thrice)-This is for avoiding nutrients and other secondary products in the mass. 

second step, dry in hot air oven at controlled temperature (at 313 K) till to complete removal of humidity in the biomass. Later, powdered it by trituration of the biomass (please avoid contamination and other chemicals and nutrients).

Then by Kbr pellet method you can find functional groups present on the biomass. Generally -NH2, C=O groups predominantly present on the fungal biomass.

Reactive Distillation.

Hi there,

We are working on those issues here at University of Ottawa. We have developed some python codes, but still waiting for a paper to be published with all the math. We are using Boltzmann distributions for internal energy calculated from the density of states (Beyer-Swineheart), calculating rate constants using the RRKM theory on DFT potential energy surfaces.  And we use temperature values in a different way as usal.

Neither. Trying to extract a protein-only total or potential energy is meaningless; it's not a free energy, which is what really tells you what happens in the physical world. The most populated state (judged from some suitable clustering analysis of the trajectory) would be more appropriate, but even then it would be hard to definitively say that it is the most stable conformer. It's potentially biased by the force field, and MD simulations are prone to being stuck in local minima, so all you can say is it is the dominant state in that particular trajectory. Perhaps other evidence will emerge based on known experimental data that you can corroborate such a claim. Multiple, long simulations and/or use of enhanced sampling techniques should be employed here to make any defensible claim.

If you are just trying to locate the TS, there are two strategies - if you can draw a reasonable TS, then do that and use opt=(ts,calcfc,noeigentest) in G09 and that should find the TS - if you can't draw what would be a reasonable looking TS, then you can use the structure of the reactant and the structure of the products in the G09 input file along with opt=(qst2,calcfc,noeigentest) and that will find a TS along a path from reactant to products - I hope this helps -

Dear Zahra,

According to Dong Zhu et al. Mn-doped ZnS quantum dots (QDs) prepared by a conventional aqueous synthetic method usually suffer from poor crystallinity and low quantum yield due to their relatively low reaction temperature. In addition, the authors of the study you mentioned stated that Curcumin caused defect-related fluorescence quenching of the probe at 458 nm, whereas the orange transition emission of the probe at 590 nm changed only negligibly with variations in curcumin concentration.

Which means that the concentration of curcumin plays dominant role in obtaining the desired dots.

Herein the study of Dong Zhu et al. entitled " Microwave-assisted aqueous synthesis of Mn-doped ZnS quantum dots and their room-temperature phosphorescence detection of indapamide" which describes the required dots using microwave:

Paper Microwave-assisted aqueous synthesis of Mn-doped ZnS quantum dots and their room-temperature phosphorescence detection of indapamide

Dong Zhu,*a Wei Li,*a Hong-Mei Wen,a Qian Chen,a Li Maa and Yue Hua

Show Affiliations

Anal. Methods, 2014,6, 7489-7495

DOI: 10.1039/C4AY01235F

Received 23 May 2014, Accepted 08 Jul 2014

First published online 09 Jul 2014

Mn-doped ZnS quantum dots (QDs) prepared by a conventional aqueous synthetic method usually suffer from poor crystallinity and low quantum yield due to their relatively low reaction temperature. In this paper, high-quality Mn-doped ZnS QDs with long-lived emissions were prepared using a green and rapid microwave-assisted synthetic approach in an aqueous solution. The QDs were used for room-temperature phosphorescence (RTP) detection of indapamide with a detection limit of 0.89 μM, and the RTP intensity showed a good linear relationship with the concentration of indapamide in the range from 1.5 to 80 μM. The relative standard deviation for seven independent measurements of 10 μM indapamide was 3.4%, and the recovery ranged from 94% to 105%.

Hoping this will be helpful,

Rafik

They all are excellent answers. Here is my experience: three equations need to be solved for three variables. A good set of three basis sets is aug-cc-pVTZ, aug-cc-pVQZ, and aug-cc-pV5Z.

Hi, Marcin

Your question is “how to find kg (gas-phase mass transfer coefficient), when gas phase is stagnant, and liquid phase is being mixed.”

My suggestion is:

1.      I have found the gas resistance cannot be neglected when the partial pressure of measured gas is very low and gas agitation is not enough, you have cited my paper in this discussion

http://www.sciencedirect.com/science/article/pii/S1876610213003408/pdf?md5=1160680935bb77de48106ac24429060c&pid=1-s2.0-S1876610213003408-main.pdf 

2.      I did not measure the k_g in the paper because I increased the gas stirrer numbers and agitation speed. Then the gas phase resistance is reduced and can be neglected.

3.      If you want to measure the k_g at stagnant gas phase, you should do two comparison experiments:

      a.  One is measuring the -dp_A/dt vs. P_A at stagnant gas phase, where the gas phase resistance cannot be neglected, you can get the overall mass transfer coefficient K_G, i.e. 1/K_G =(1/k_g + He/k_L)

      b.  The other is measuring the -dp_A/dt vs. P_A at good gas phase agitation, where the gas phase resistance can be neglected, you also can get the overall mass transfer coefficient K’_G, i.e. 1/K’_G =(0 + He/k_L)

      c. HE/k_L in the two equations could be equal when the agitation speeds are same, then comparing the two results, you will get k_g you asked.

4.      The method you can refer to my thesis (I think you have got it), page 131, equation (7.26 - 7.29) or the paper

      Industrial & Engineering Chemistry Research 52(7):2548–2559

Hope it’s useful for you :)

you can determine bioaccumulation by TEM, SEM - EDX and XRF.

Dear Samira,

You may use the following link for getting data of some of the listed compounds.

Good luck,

Rafik

The short answer is that many heat shock proteins are molecular chaperones.  The function of this class of proteins is to help other proteins fold into their native state, or correct 3D structure.  This has led to the idea that the primary damage that occurs from increased temperature and many chemicals is disruption of protein folding.  Therefore, the heat shock response increases the levels of molecular chaperones and enables cellular proteins to maintain their correct structure even with increased temperature or other stresses.   

Thanks alot

Dear Anas Alkhazelah,

I think you can calculate the temperature of the solution after pumping in RO process theoretically by doing energy balance on the system.

I hope my explanation can help you.

It will be the total electron density of the valence electrons as obtained from the POTCAR file. For example, if you grep "ZVAL" for the Ti_pv PAW POTCAR file, you will see that the potential has 10 electrons explicitly included for each Ti atom. The remaining 12 are approximated by the PAW projectors. You can check this in your calculations. If you grep "NELECT" in the OUTCAR file, the number of electrons that is given are the total number of explicitly treated valence or semi-core electrons, not the total number of electrons in the real system.

Thanks Jean-Francois. I think I could try piranha solution for steel substrates and sodium hypochlorite solution on organic substrates.

Hello,

I think that the reason of of formation of empty-space-regions after your 1st doctor-blading - is caused by impurities on substrate (like fatty/oily regions - where the wettability is reduced). That's why even if you try to "cure" the defects by 2nd run of doctor blade - there will be no success. [even if abter 2nd doct.-blading you will be able to fill the defective places - the structure at the boundaries formed between 1st layer and filled layer - will for sure be different. [of course the same (of impurities) problem can occure on the doctor-blade-itself...   Regards,     Leonid

First, let me stress that the activation energy is not a well defined microscopic quantity, but a convenient parameter in which we can hide our ignorance on the details of the many different possibilities for the individual reactions. 

This having been said, the importance of quantum effects at a given temperature can be assessed by comparing the corresponding thermal energy with the characteristic energies for the different statistics, that is, the zero point energy for enclosing the particle in a given volume, which, for Fermions is known as the Fermi energy and for Bosons as the condensation energy.

As an example, let us take the Fermion case. For electrons in sodium metal, with a particle density of 2.65 x 10^28 /m^3, the Fermi energy is 3.24 eV and the Fermi temperature is 37'700 K, proportional to (N/V)^(2/3) and inversely proportional to the mass of the particle. I am not an expert in solution chemistry (if the concept makes sense  at all at such low temperatures), but I think it is fair to assume that, just on steric grounds, the number density of the reacting molecules is at least two orders of magnitude smaller, which divides the sodium result by a factor of the order of 20. Then, we know that the mass of the nucleon is 1836 times larger than that of the electron, and already for a small molecule like methane, this means division by further factor, this time of the order of 30'000. So you see that the degeneracy temperature at which quantum effects become important is below 0.1 K. Exactly the same reasoning holds for the boson case.

In summary, there is no need to change anything in your treatment.

Best regards, René Monnier