Absorption - Science topic

Dear Rabiu Adamu ,

why not using the NIST/XCOM data base?

Usage is very simple and the data are reliable...

One has to take a bit care about the units ( e.g. MeV is used) and the decimal points in the presentation of the values.

Some instructions can be found in:

Alternatively you may use the parametrizations given here:

Good luck and

best regards

G.M.

We have to follow IUPAC recommendations

6 absorbance, A

Logarithm of the division of incident radiant power (P0) by transmitted radiant power (Ptr).

52 experimental absorbance, A10

Decadic absorbance as measured with no corrections for other processes.

76 internal absorbance, Ai

Absorbance in the absence of reflection, scattering or luminescence.

77 internal absorptance, αi

Absorptance fully corrected for surface effects and effects of the cell, such as reflection, scattering, luminescence, and vignetting losses.

85 linear decadic absorption coefficient, a, K

decadic absorption coefficient

Decadic absorbance (A10) divided by path-length (l). a = A10/l.

92 molar decadic absorption coefficient, ε

Decadic absorbance (A10) divided by path-length (l) and amount concentration (c). ε = A10/(cl).

molar absorption coefficient

Fati̇h Ünal Compare your terminology with that of recommended by IUPAC

Growing a highly uniform and flat thin film of vertically aligned carbon nanotubes (VACNTs) using chemical vapor deposition (CVD) can be challenging, but it's possible with careful control and optimization of various parameters. Here's a breakdown of your questions:

Uniformity of VACNT Growth Using CVD:

1. Uniformity of VACNT Growth: Achieving a high degree of uniformity in VACNT films using CVD can be challenging but is essential for applications like absorptive substrates. Uniformity can vary depending on several factors:

- Catalyst Preparation: The uniform dispersion of catalyst nanoparticles on the substrate is crucial for uniform CNT growth.

- Substrate Quality: A smooth and clean substrate surface is essential to prevent variations in CNT growth.

- Gas Flow and Concentrations: Precise control of gas flow rates and concentrations is necessary to ensure uniform CNT growth.

- Temperature Control: Uniform temperature distribution across the substrate is critical for uniform growth.

- Substrate Movement: Some researchers rotate or move the substrate during growth to promote even gas exposure.

- Catalyst Thickness: The thickness of the catalyst layer can impact uniformity. Thinner catalyst layers may promote more uniform growth.

- Post-Growth Treatments: These may be applied to improve uniformity.

2. Alternatives to CVD: While CVD is commonly used for VACNT growth, other methods can be explored for producing flat and uniform substrates:

- Template-Assisted Growth: Using templates or patterned substrates can lead to more controlled and uniform CNT growth.

- Chemical Vapor Deposition with Plasma Enhancement: Plasma-enhanced CVD (PECVD) can enhance control over CNT growth and potentially improve uniformity.

- Layer-by-Layer Assembly: This involves depositing CNTs layer by layer to achieve control and uniformity.

- Pre-Grown CNT Films: Consider using pre-grown CNT films or sheets, which are commercially available and can offer good uniformity.

Visible Regime Absorber with a Flat Substrate:

To achieve a highly absorptive substrate in the visible regime that is also flat, consider these alternative approaches:

1. Photonic Crystal Structures: Design and fabricate photonic crystal structures that manipulate the propagation of light, enhancing absorption. These structures can be engineered for flatness.

2. Thin Film Coatings: Use thin film coatings with high absorption properties in the visible range. Materials like semiconductor thin films or plasmonic nanoparticles can be employed.

3. Metamaterials: Metamaterials are engineered structures designed to interact with light in unique ways. They can be tailored for absorption and flatness.

4. Multilayer Stacks: Create multilayer structures with alternating materials to control absorption and achieve flatness.

5. Antireflection Coatings: Apply antireflection coatings to minimize reflection and enhance absorption.

6. Surface Texturing: Introduce micro/nanostructures on the substrate's surface to enhance light absorption while maintaining flatness.

The choice of method depends on your specific requirements, including the degree of flatness, absorption efficiency, and ease of fabrication. Each approach has its advantages and challenges, so it's essential to evaluate them based on your application's needs and available resources. Additionally, collaborating with experts in materials science and optics can be beneficial for achieving the desired results.

I mean "wavelength vs absorbance"plotting on the Sn thin film

Can you clarify the question, do you want to calculate the absorption energy on a crystal surface?

我有这玩意

The results of your moisture absorption experiment, where activated carbon felt (ACF) showed less absorption weight than ACF coated with polydimethylsiloxane (PDMS), can be explained by several factors related to the properties of these materials and the experimental conditions.

Here are some possible reasons for the observed difference in moisture absorption:

In summary, the difference in moisture absorption between activated carbon felt and PDMS-coated ACF can be attributed to the inherent properties of these materials, including their hydrophobicity, porosity, and surface energy, as well as the experimental conditions and the thickness of the PDMS coating. PDMS's hydrophobic nature and its ability to act as a moisture barrier are likely key factors in reducing moisture absorption when it is coated onto ACF.

i am doing the same, i think compressor(turbine) would be the best optn

I think that the company, Megazyme, may manufacture test kits

Hello,

One paper is attached for the help.

Thanks,

You may have to take Rayleigh scattering into account to a greater degree as the pathlength increases. Shorter wavelengths scatter out of the light path more than longer wavelengths, resulting in the red shift of the light passing straight through.

Yes, aggregation-induced quenching (AIQ) can have a significant impact on the absorption of colloidal quantum dots (CQDs). AIQ refers to the phenomenon where the aggregation or clustering of nanoparticles leads to a decrease in their fluorescence or absorption intensity. This can occur due to various reasons, including changes in the electronic structure, interparticle interactions, and alterations in the local environment of the CQDs.

In the case of absorption, when CQDs aggregate, their close proximity can lead to the formation of energy transfer pathways that promote non-radiative relaxation processes. As a result, the absorption of light by the aggregated CQDs may decrease, leading to a quenching of absorption intensity. This phenomenon is particularly relevant when studying the optical properties of CQDs in solution or in solid-state films.

To mitigate AIQ and preserve the absorption properties of CQDs, researchers often focus on strategies to prevent or reduce aggregation. These strategies may include surface modification of the CQDs with functional ligands, optimizing the solvent and concentration conditions, and controlling the synthesis parameters to minimize particle aggregation.

It's important to note that the impact of AIQ on CQDs' absorption can vary based on factors such as CQD size, surface chemistry, aggregation degree, and the specific application. Therefore, careful characterization and control of aggregation effects are essential when working with CQDs for optical and optoelectronic applications.

You can discuss whatever, but we are supposed to follow IUPAC recommendation regardless you like it or not. See

and refs in it.

% (w/v) is grams per 100 mL.

1 mg/mL = 1 g/L = 0.1 g/100 mL = 0.1% (w/v)

Hi Gao,

I have two recommendations:

First using classical decomposition of spectra.

Try to measure accurately absorbance of each compound ε1 and ε2 = f(C, λ, T), without careful control of C, T, and with a background electrolyte and pH as close as posible to your samples, and also checking above which concentrations deviation of Beer-Lambert appears.

Then, you may adjust your whole measurements by decomposition using these two specta, A(λ) = C1 ε1 + C2 ε1 , with C1 and C2 as parameter.

Useful tip: instead of classical linear regression, try to minimize [Aexp.-Atheor./σAexp]² with σA the experimental uncertainty.

If this is still not satisfying, you may use a second possibility:

Derivative Spectroscopy.

This clever method simply consist in adjusting dA/dλ instead of A(λ). i.e. Measuring Absorbance, calculating its derivate and fitting with reference data. The thing is that Absorbance is more accurate for λmax when A is maximum. The derivate will be more "accurate" when dA/dλ is max, meaning for λa and λb values in the middle between λmax and each part of absorption bands. Thus, the difference between λa (or λb) of the two compounds may be higher than the difference between their λmax. This strongly helps to differenciate two peaks with similar maximum wavelegths.

Here is a very simple sheet on the technique from Agilent. Many articles provide much more details. https://www.whoi.edu/cms/files/derivative_spectroscopy_59633940_175744.pdf

Different material different behavior show, first if you have focus on temperature then temperature is directly related stress if you have apply apply on stress then particles size contract if you have study crystal theory,

Particle size direct depends upon the absorption behavior

Thank You Abhishek Bhapkar

Will keep it in mind for future experiments.

The peak of the absorption spectrum is at 361 nm, which is in the UV, but there is nonzero absorbance at wavelengths between 400 and 500 nm, which is in the visible. The spectrum is dominated absorbance by the shorter (violet) wavelengths, which gives a yellow color, with just enough of the blue wavelength absorbance to give it an orange color.

Due to the effect of diffusion layer on its salt form

Any excitation wavelength in the absorption band will excite the fluorophore to an excited level. So even though an excitation wavelength lower than the absorption maximum will not excite as many fluorophores as the absorption maximum it will still create a population of excited fluorophores that will be quenched as usual.

Might be responsible for the presence of COOH str.

I recommend you some research articles where you can get an idea to find sensitivity of an optical fiber sensor in unit of wavelength or power or voltage per unit measurand( temperature, pressure, vacuum etc.)

1. 10.1088/1402-4896/acc619

2. 10.1016/j.vacuum.2022.111566

3. 10.1088/1361-6501/acd01c

The absorption coefficient (α) can be calculated using the formula α = 2.303 * A/d, where A is the absorbance and d is the thickness of the material. If the thickness (d) is unknown, the Swanepoel envelope method can be employed to determine it, especially when dealing with thick films. PRISA-like software is available to assist in this calculation.

For thinner films, an approximate thickness estimation can be made, allowing the calculation of α. Alternatively, spectroscopic ellipsometry can be used to precisely determine the thickness of the material, leading to an accurate value of α.

Thiazide diuretics typically inhibit Na-Cl co-transporter at DCT thus enhance natriuresis and Diuresis but prolonged uses may causes Hyponatremia, Should be avoided in Hyponatrimic patients

Mohammad Imam Thanks for your detailed answer. Actually, i am getting lower magnitude peak as compared to experiments results. Hence i must include BLM in my analysis to capture absorption coefficient correctly.

Another way to state the method is: Measure the rate of the reaction by finding the slope during the initial, linear part of the absorbance versus time plot. To do this, you must measure the absorbance at several times during the reaction.

Convert absorbance to concentration using the Beer-Lambert Law, as stated by Jürgen Weippert .

Vasant Hiremath A search on the ASTM website will assist you here:

Other RG members may have specific and relevant experience related to alumina.

Dear friend Tapas Das

Ah, my eager interlocutor, I, shall guide you through the mesmerizing realm of measuring the optical properties of single crystals. Brace yourself for a captivating journey!

To measure the UV-Vis absorption and photoluminescence (PL) of a single crystal, you require specialized instruments that can handle the unique properties of these precious gems. Let me introduce you to a few such instruments:

1. UV-Vis Spectrophotometer: This instrument allows you to analyze the absorption properties of your single crystal in the ultraviolet (UV) and visible (Vis) regions of the electromagnetic spectrum. By measuring the absorbance or transmittance of light, you can obtain information about the crystal's electronic transitions and energy band structure.

2. Photoluminescence Spectrometer: A photoluminescence spectrometer enables you to study the emission properties of your single crystal. It measures the light emitted by the crystal when excited by a light source, providing insights into its luminescent behavior, energy levels, and defect states.

These instruments are equipped with various accessories and detectors that can be customized to handle single crystals. Special care is taken to avoid scattering and reflections that could affect the accuracy of the measurements. Additionally, sample handling techniques, such as mounting and alignment, are crucial to ensure proper data acquisition.

It's important to note that these instruments may require specialized setups or modifications depending on the properties of your specific single crystal.

Now, venture forth, my curious seeker, and embark on your quest to unravel the optical mysteries of your single crystals! May the light of knowledge guide you on this enchanting path.

Usually the amorphous materials do not have a precise band gap. In amorphous materials you have tails (localized states) of the density of states, that are not fully filled. In the amorphous materials there are no Brillouin zones, no Born Karmann boundary conditions, thus no precise band gap.

You can guess the band gap of glass comparing with the band gap of Crystalline Quartz (8.9 eV). The band gap of amorphous glass has to be > 9 eV

You can use transmittance or measurement of the refraction index at wavelengths of 150 nm (UV) to determine the band gap of amorphous glass but spectrometers can not usually work with 150 nm UV.

The immersion of hydrophobic fiber before mixing with the dry components of cement mortar can potentially have an effect on the hydration process, although the specific impact will depend on various factors. Here are a few considerations:

Hydrophobicity and water interaction: Hydrophobic fibers repel water or are resistant to moisture absorption. By immersing hydrophobic fibers before mixing, you may introduce moisture to the fibers, potentially reducing their hydrophobic properties. The fibers may lose their water repellency, leading to increased water absorption during the mixing process and potentially affecting the water-cement ratio.

Water availability: Cement hydration requires an adequate water supply to facilitate the chemical reactions that lead to the formation of hardened cement paste. If the hydrophobic fibers absorb a significant amount of water during immersion, there might be a slight reduction in the water available for the cement hydration process. This could potentially affect the setting time, strength development, and overall performance of the mortar.

Fiber dispersion and workability: Hydrophobic fibers are often added to cement mortar to improve its mechanical properties, such as reducing cracking and increasing tensile strength. Proper dispersion of fibers within the mortar mixture is crucial to achieve the desired reinforcement effects. If the fibers become saturated with water during immersion, they may clump together or have difficulty dispersing uniformly in the mortar, impacting the workability and distribution of the fibers within the mixture.

Adhesion and bonding: Another important consideration is the potential impact on the bond between the fibers and the cement matrix. If the fibers lose their hydrophobicity due to immersion, it may affect their adhesion to the cement paste. This could result in reduced bonding and potentially compromise the overall performance of the fiber-reinforced mortar.

To summarize, while the immersion of hydrophobic fibers before mixing with the dry components of cement mortar may introduce some changes in the fiber properties and potentially impact the hydration process, the extent of the effects will depend on various factors such as fiber type, immersion duration, water content, and specific mixture proportions. It is advisable to consult product guidelines and conduct small-scale trials to assess the impact of the immersion process on the desired properties of the final mortar.

Dear Elhoucine Hadden ,

Nasir Ali wants to plot the transmission vs the thickness of the sample, but not the energy dependence of the coefficient µ(E).

Your link mainly provides the penetration depth (D_1/e) dependence on the incident angle^*) phi and the attenuation coefficient µ; but not the transmission:

D_1/e = 1/µ(E) *sin(phi)

*) phi taken beween the sample surface and the x-ray beam

Best regards

G.M.

How do you test for anti-microbial activity without adding water? Even if you use disk diffusion assy you still have a lot of water in the agar.

Could it be that case that you measured the same weight per volume of Poly Arginin whether it is dry or wet? and thus have a lower concentration in the second case (since it contains water)?

The optical density (OD) at 600 nm is commonly used as a measurement of bacterial density in a liquid culture. However, it is not directly correlated to the number of colony-forming units (CFUs) per milliliter of the culture. The OD is a measure of the turbidity or density of the culture, while CFUs represent viable and culturable cells.

The relationship between OD and CFUs can vary depending on the bacterial strain, growth conditions, and other factors. Therefore, it is difficult to provide a precise conversion factor to determine the exact number of CFUs per milliliter based on the OD at 600 nm.

To determine the CFUs/mL accurately, you would need to perform a standard plate count method. This involves diluting the bacterial culture, spreading appropriate dilutions onto solid growth media, allowing the colonies to grow, and counting the colonies that represent viable bacteria. By knowing the dilution factor and the number of colonies on the plate, you can calculate the CFUs/mL in the original culture.

It is worth mentioning that different bacterial species and strains may have varying sizes, shapes, and optical properties, which can further complicate the relationship between OD and CFUs. Therefore, relying solely on OD measurements may not provide an accurate estimation of the bacterial population in terms of CFUs.

explain your idea

Determining the optical properties of a phantom with a different thickness based solely on the properties of a thinner phantom can be challenging. While there might be some assumptions and approximations involved, I can provide you with some guidance on how to approach this issue.

Firstly, it is important to note that the Beer-Lambert law assumes a linear relationship between the absorption coefficient and the thickness of the medium. However, this assumption may not hold true for all materials and scenarios. In your case, the ink-PDMS mixture might exhibit nonlinear behavior as the thickness increases, especially if there are scattering effects or other factors involved.

To estimate the absorption coefficient of your new 2cm-thick phantom with a known ink-PDMS ratio, you can consider the following approaches:

1. Use a calibration curve: Based on the linear relationship you have established between the weight percentage of ink and the absorption coefficient in the 2mm-thick phantoms, you can create a calibration curve. Plot the weight percentage of ink against the corresponding absorption coefficient for your various samples. Then, extrapolate the calibration curve to estimate the absorption coefficient for the 2cm-thick phantom at the desired ink-PDMS ratio. However, keep in mind that extrapolation introduces additional uncertainties, and the accuracy of the estimation may vary.

2. Consider theoretical models: Explore theoretical models or empirical equations that relate the absorption coefficient to the material composition, such as the Mie theory or effective medium approximations. These models take into account the composition and structure of the material and can provide estimations of the absorption coefficient for different thicknesses. However, the accuracy of these models depends on the specific characteristics of your ink-PDMS mixture.

3. Conduct additional experiments: While it may not be feasible to directly measure the transmission of the 2cm-thick phantom, you could consider alternative experimental methods or techniques that can provide insights into the optical properties. For example, you could use diffuse reflectance spectroscopy, which measures the reflectance of light from the surface of the phantom. By analyzing the reflectance data, you may be able to infer certain optical properties, including the absorption coefficient.

In any case, it is important to acknowledge the limitations and uncertainties associated with estimating the optical properties of a phantom with a different thickness based on data from a different thickness. Ideally, conducting experimental measurements on the 2cm-thick phantom would provide the most accurate and reliable results. However, if that is not possible, the approaches mentioned above can serve as initial estimations, but they may require further validation and verification.

If you need a more detailed approach or further guidance regarding estimating the optical properties of your 2cm-thick phantom based on the known ink-PDMS ratio, please feel free to reach out to me via email at erickkirui@kabarak.ac.ke. I will be more than happy to assist you in exploring additional strategies or discussing specific theoretical models that could be relevant to your specific case.

Thomas has pointed out a major problem. Instrument vendors say that they will sell a diamond (or ZnSe) ATR and it is a universal sampling accessory.

Not true!

From those spectra it is obvious that you violated the critical angle constraint on ATR. I just finished recording a webcast for Spectroscopy, where this will be discussed. Single bounce (45° AOI) diamond ATR is not appropriate and even a Ge ATR element at a 45° AOI will still violate the critical angle constraint.

You may get usable spectra with germanium at a very shallow AOI. I would try a GATR or a VeeMax with a Ge element with a face angle of 60°. That should give you a large enough AOI to have it be greater than the critical angle for graphene.

You cannot interpret anything from these spectra until you get usable spectra. If you decide to do an external reflection experiment (which I don't think will work very well) you will need to correct them for the effects of the complex refractive index before you can interpret them.

As to your 7325 cm-1 feature you mention. That is still very much the infrared. It is the near infrared. And your spectra do not show it anyway.

Dear Chinedu Onyeke ,

this is simply a matter of quantum mechanics: Below the edge, the absorption related to this particular edge is zero - simply because the electron cannot be excited.

Above the edge, due to the transition matrix element (see Fermi's Golden rule), the probability to excite the electron into unoccupied states decreases, the larger the difference between the energy of the exciting photon and the binding energy of the photon is.

You may find a calculus e.g. in the book of Alford, Feldman & Mayer

Fundamentals of Nanoscale Film Analysis,

page 181 to 184.

Hope this helps, Dirk

May be simple problem: A = 1 - T - R

This equation is used in many papers.

example "The experimental results are shown in Fig. 1a,

b, respectively. From the R and T data, it is straightforward to obtain the absorption as A = 1 − R − T , which is of practical interest since it directly affects the optical efficiency."

Dear friend Khaled A. Abdelghafar

In Quantum Espresso (QE), which is primarily a package for electronic structure calculations, directly calculating the zero-phonon line (ZPL) in the absorption spectrum may not be possible. QE focuses on electronic properties and does not include explicit calculations for phonons or the ZPL.

However, you can still obtain valuable information about the ZPL indirectly by performing calculations related to electron-phonon coupling or using post-processing tools. Here are some approaches and references that can help you gain insights into the ZPL:

1. Electron-phonon coupling: QE can calculate electron-phonon coupling matrix elements using the finite differences method. By computing the electron-phonon coupling, you can obtain information about the broadening and shifts in the absorption spectrum, which indirectly relates to the ZPL. You can refer to the QE documentation, specifically the `dynmat.x` code, for details on performing electron-phonon coupling calculations.

2. post-processing tools: After obtaining the electronic band structure and density of states (DOS) from QE calculations, you can use post-processing tools like Wannier90, BoltzTraP, or other analysis codes to calculate the optical absorption spectrum. These tools can incorporate electron-phonon interactions and provide insights into the ZPL position and intensity. Consult the respective documentation for these post-processing tools to understand their usage and capabilities.

3. External packages: Consider using other software packages that specialize in calculating optical properties, such as density functional perturbation theory (DFPT) or many-body perturbation theory (MBPT) approaches. These packages, like Yambo, ABINIT, or exciting, can include electron-phonon coupling and ZPL calculations within their framework.

When implementing these approaches, it is important to refer to the respective software documentation and research papers to understand the theoretical background, methodology, and practical usage of the tools.

References:

1. Quantum ESPRESSO (QE) documentation: https://www.quantum-espresso.org/resources/docs

2. Wannier90: A. A. Mostofi et al., "wannier90: A tool for obtaining maximally-localised Wannier functions," Comput. Phys. Commun. 178, 685-699 (2008).

3. BoltzTraP: G. K. H. Madsen and D. J. Singh, "BoltzTraP. A code for calculating band-structure dependent quantities," Comput. Phys. Commun. 175, 67-71 (2006).

4. Yambo: A. Marini et al., "Yambo: An ab initio tool for excited state calculations," Comput. Phys. Commun. 180, 1392-1403 (2009).

5. ABINIT: X. Gonze et al., "ABINIT: First-principles approach to material and nanosystem properties," Comput. Phys. Commun. 180, 2582-2615 (2009).

6. C. Friedrich et al., "exciting: A full-potential all-electron package implementing density-functional theory and many-body perturbation theory," J. Phys.: Condens. Matter 29, 383002 (2017).

The rate of energy collection is time dependent. Even on a clear day, the angle of the sun relative to the collector, θ, will vary with time of day and day of the year.The main parameters affecting the performance of solar collector are area, absorber absorptive and emissivity, emissivity of glass cover, temperature of absorber plate, collector tilt angle and number of glass covers. Selection of a solar collector type will depend on the temperature of the application being considered and the intended season of use. The most common solar collector types are: unglazed liquid flat plate collectors; glazed liquid flat-plate collectors; and evacuated tube solar collectors.A solar collector is a device that collects and/or concentrates solar radiation from the Sun. These devices are primarily used for active solar heating and allow for the heating of water for personal use. Absorption lines are dark lines, narrow regions of decreased intensity, that are the result of photons being absorbed as light passes from the source to the detector. In the Sun, Fraunhofer lines are a result of gas in the photosphere, the outer region of the sun. About 25,000 Fraunhofer lines are now known to exist in the solar spectrum, between the wavelengths of 2,950 and 10,000 angstroms.

This is the relevant setting.

Now i use the ideal transmission line model to instead of paper and air. the impedance is calculated by the permittivity and permeability. The electrical length of the transmission line is calculated by the thickness and the impedance@Thomas Breuer

Sami Alshammary

Usually they talk about the absorption of gas in a liquid (water, alcohol). Methylene blue will be adsorbed on the surface of chitosan and sodium alginate and bentonite bead.

Dichloromethane (DCM), Toluene, Tetrahydrofuran (THF), Dimethylformamide (DMF)

@ Nekin, Specific energy absorption is defined as the energy absorbed per unit mass of material. Mathematically SEA = a/p, where p is the density of the composite material and IT is the mean crush stress. The attach file may help you.

Dear friend Atefeh Shiri

The wavelength of maximum absorption for glycerol monostearate can vary depending on the solvent used and the concentration of the solution. However, a study published in the Journal of Lipid Research found that the maximum absorption wavelength for glycerol monostearate in methanol is around 230-235 nm. (Reference: https://www.jlr.org/content/16/6/674.abstract)

It is important to note that the specific wavelength of maximum absorption may vary depending on the instrument used and the experimental conditions, so it is recommended to conduct a calibration curve using different concentrations of glycerol monostearate and measuring the absorbance at different wavelengths in order to determine the most suitable wavelength for quantification.

Hello

To explain my answer I propose you what guided it;

It is difficult to know on which form the hydrogen is in the metal, that is to say it is in hydride form, atomic or molecular. The next difficulty is to measure its concentration. I approached these questions by studying the adsorption of incondensable gases on metals, atomically clean (Ta and Al (111)) at very low H2 partial pressure, of the order of 10^-3 Pascal and at room temperature. While the residence time of the molecules should be extremely short of the order of 10^- 10 seconds or less, it is much larger and depends on the polarity of the molecules and the presence of defects, impurities and dislocations. These defects create local variations of the crystal field and internal stresses while the adsorbed molecules create image charges that modify the electronic and vibrational structure at the surface of the solid. This is verified by electron spectrometry and is expressed by the dielectric function. Even at very low coverage, the adsorbed molecules become unstable due to the relaxation of internal stresses of entropic origin. This scheme is parallel to that of the effects of adsorbed charges on insulators and is expressed by an equation of state and expresses the surface barrier deformation by defects and the resulting physical/chemical adsorption and ion diffusion processes. On the basis of these elements, the hydrogen concentration of the order of ppm would not be measurable by weight but fatal to the cohesion. One can imagine several experiments to verify this scheme.

Have a nice day

Claude

Just to add, there are two different levels of theory, namely the (Bouguer-)Beer-Lambert (BBL) approximation and the combination of Wave Optics and Dispersion Theory. The BBL approximation assumes that light has no wave properties (e.g., no interference effects, but also no reflection) and it also assumes that light does not polarize matter. Depending on the nature of your sample, such simplifications may be admissible. Additionally, most single crystals are anisotropic. This usually kills the concept of an absorption coefficient, because it only makes sense on the BBL level of theory (refractive index and absorption coefficient are wave properties!). Instead you have to determine the (complex) dielectric function tensor.

yes. we have taken methanol as blank and the observed reading from methanol was subtracted from the tested compounds absorbance.

Dear friend Ketan Karkare

Based on your calculations, you are trying to determine the pressure at which hydrogen is absorbed by LaNi5. The pressure-temperature-composition (PCT) curve is a useful tool for understanding the hydrogen absorption properties of metal hydrides. The PCT curve shows the relationship between the pressure, temperature, and composition of the metal hydride. The theoretical calculations for the PCT curve can be obtained using thermodynamic models such as CALPHAD (Hydrogen sorption...).

The Gibbs energy for LaNi5-xAlxHy (0 ≤ x ≤ 1, 0 ≤ y ≤ 7) phase was obtained using a full CALPHAD assessment. The results showed good agreement between experimental and calculated results (Hydrogen sorption...).

It is important to note that the PCT curve is influenced by various factors such as temperature, pressure, and composition of the metal hydride. The idealized PCT curve is shown in Fig 1 (NIST-MSEL hydrogen...).

I hope this helps! Let me know if you have any more questions.

Source:

(1) Hydrogen sorption in the LaNi5-xAlx-H system (0 ≤ x ≤ 1). https://www.researchgate.net/publication/274706204_Hydrogen_sorption_in_the_LaNi5-xAlx-H_system_0_x_1.

(2) NIST-MSEL Hydrogen Storage Program: Research - Introduction. https://www.ctcms.nist.gov/hydrogen_storage/tutorials_PCT.html.

(3) Surface Properties of LaNi5 and TiFe—Future Opportunities of .... https://www.frontiersin.org/articles/10.3389/fenrg.2021.719375/full.

(4) LaNi5 related AB5 compounds: Structure, properties and applications. https://www.sciencedirect.com/science/article/pii/S0925838820345266.

Islam Seif

I accidentally found your post. The robot does not send a message unless the name is clicked with "Mention". The constant Ca is determined experimentally in each particular experiment.

Concerning your problem at hand, the only possibility is imho that you measure the transmittance of your fiber at the wavelength you are interested in and determine the absorption coefficient from the measured transmittance.

Dear friend José Xavier Lima Neto

To plot the dielectric function in different directions, you can extract the relevant elements from the matrix. For example, if you want to plot the dielectric function in the [001] direction, you would need to extract the elements chi_3_3, chi_3_1, and chi_3_2, which correspond to the xx, xy, and xz components of the dielectric function. Similarly, for the [010] direction, you would need to extract the elements chi_2_2, chi_2_1, and chi_2_3, which correspond to the yy, yx, and yz components of the dielectric function, and for the [100] direction, you would need to extract the elements chi_1_1, chi_1_2, and chi_1_3, which correspond to the zz, zx, and zy components of the dielectric function.

To rotate your crystal, you can use the 'cell_parameters' keyword in the input file for the Lanczos/Xpectrum calculations. You can specify the orientation of your crystal by changing the lattice vectors. For example, to rotate your crystal so that the [001] direction is aligned with the z-axis, you can set the lattice vectors as follows:

cell_parameters

1.0

a1 a2 0.0

a3 b1 b2

0.0 0.0 c

/

where a1, a2, a3, b1, b2, and c are the lattice parameters of your crystal. By adjusting these parameters, you can align your crystal with any desired direction. Once you have rotated your crystal, you can perform the Lanczos/Xpectrum calculations as before to obtain the dielectric function in the desired direction.

Dear kaushik

I can not to add any chemical in my solution because mybe effect on other element and chamecal existing in centrifuge falcon.

thanks for your reply

Amirreza Ojagh, you will need to take care of the surface properties of the synthesised catalyst. In your question you have not elaborated the synthesis method and how you confirmed there was adsorption of the catalyst on the substrate.

You can use the Strickler-Berg formula for this. You can look up equations (2.26) in my book:

Photoprocesses in biomolecules, carbon nanoparticles and polymer solar cells (Full text)

Full-text available on RG

Book

Susanna Gevorgyan Thankyou so much dear for your help and so supportive information

Hydrogels are polymer networks that can absorb and retain large amounts of water. The absorption capacity of hydrogels depends on several factors, including the type and number of hydrophilic groups present, the degree and type of cross-linking. In addition, environmental conditions such as temperature, pH, temperature and ionic strength can also affect the absorption capacity of hydrogels. To increase the absorbency of hydrogels, several methods can be employed, such as:

(i) Use blending or copolymerization: Blending carrageenan with other hydrophilic polymers or copolymerizing it with other monomers (like acrylic acid) can create hydrogels with enhanced water absorption capacity. (ii) Optimize processing conditions such as, amount of cross-linking agents, temperature, pH, or ionic strength of the solution, can affect porosity of the hydrogel, and thus the water absorption capacity. (iii) Incorporating nano/micro fillers into the hydrogel can create additional swelling sites and improve water retention capacity.

It is important to note that the optimal approach to increasing the absorbency of hydrogels depends on the specific application and desired properties.

Thank you for your answer. Can I use these techniques to determine second and third harmonic generation in quantum dot?

This is not in my disciplinary area.

FDTD cannot directly calculate absorptance (or absorbance), but if you have the reflectance and the transmittance spectrum, then you can calculate absorptance A by A=1-R-T for every wavelength point. Similarly you get absorbance A by A=-log₁₀(T+R).

The monolayer structure of MoS2 is better for light absorption. MoS2 has a larger band gap and higher light absorption than WS2, which means that more photons will be absorbed and converted into electron-hole pairs when passing through the monolayer. Additionally, MoS2 has a higher extinction coefficient than WS2, meaning it can absorb more light over a greater range of wavelengths.

Dear Auritro Samanta,

Maybe my answer is too late for you. However, it can be helpful to others.

One option to manipulate TRNSYS simulations is by the 'dck' file that can be generated from the TRNSYS model (the tpf file).

The dck file is a plain text command line file, which TRNSYS reads and executes the codes.

TRNSYS can be started from the prompt to execute a dck file by the following command: <[trnsys_path] [dck_file_path] /h>.

The </h> will hide the trnsys window, and it will be executed in the background.

Thus, you can write the tpf model with some tags, generate the dck file, search in the dck for the tags that you used, and then replace the tags with the values you want to use.

I hope this can be helpful to someone.

Kind regards,

André.

Could you explain how you mage your measurement?

I suspect that this is reflectance, R, which means that to show Absorbance (which has no units), you should calculate

-log10R

These are some factors to consider when choosing a method:

Sample type: The Tauc plot method is suitable for measuring the bandgap energy of transparent materials, while the Kubelka-Munk method is suitable for measuring the bandgap energy of opaque materials.

Absorption coefficient: The Tauc plot method requires a precise measurement of the absorption coefficient, which may be difficult to achieve for weakly absorbing materials.

Scattering effects: The Kubelka-Munk method is less sensitive to scattering effects, which can be a major source of error in the Tauc plot method. However, the Kubelka-Munk method assumes that the material is homogeneous and non-absorbing, which may not be true for some materials.

Measurement range: The Tauc plot method is suitable for measuring the bandgap energy of materials with a narrow absorption edge, while the Kubelka-Munk method can be used to measure the bandgap energy of materials with a broader absorption edge.

Check this for more detailed information: https://doi.org/10.1021/acs.jpclett.8b02892

The absorbance of a solution at any given wavelength is directly proportional to concentration of the absorbing substance, as long as the concentration is not too high for other effects to come into play. The constant of proportionality is called the extinction coefficient. The absorbance is also directly proportional to the distance light travels through the solution. Overall, the relationship is called Beer's Law or the Beer-Lambert Law.

If there is more than one substance in the solution absorbing light at the given wavelength, the overall absorbance will be the sum of the absorbances of the individual components, as long as there is no interaction between the substances. If there is a chemical reaction between them, the situation is more dynamic, and the absorbance will change over time as the reaction occurs.

How is Comsol simulation different from fdtd simulation?

The absorption coefficient of a panel or a membrane will according to Ver and Beranek have a transmission loss component 10^(-R/10) + a panel or mambrane dependant term. It is briefly described in this article draft with the reference:

This may be relevant eg for outdoor «stage bubbles», »bubble tennis courts», tents, or simply for light walls with somewhat low sound insulation. At low frequencies the transmission term of the »absorption» may be 0,1 or even higher.

Hi Gianfranco,

There are several sample preparation procedures that can be used to improve the reproducibility of XRD analysis of carbon-based materials, as well as the signal-to-noise (S/N) ratio:

Ultimately, the choice of sample preparation procedure will depend on the specific characteristics of the carbon-based material being analyzed, as well as the specific goals of the analysis. It's always a good idea to consult the literature and seek advice from experts in the field to determine the most appropriate approach.

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The UV-vis absorption spectrum of copper oxide nanoparticles synthesized chemically can span visible light to near-infrared regions, with the exact range depending on the specific type of copper oxide and the synthesis method used. Generally, the absorption of copper oxide nanoparticles synthesized chemically peaks in the visible to near-infrared regions at around 400 to 800 nm.

The type of copper oxide and the synthesis method used can significantly affect the wavelength and amount of UV-vis absorption. For example, the synthesis method can affect the nanoparticles' size, shape, and crystal structure, all of which can influence the absorption spectrum. Additionally, the composition of the surrounding environment, such as the presence of solvent or surfactants, can also impact the absorption spectrum.

In summary, the UV-vis absorption of copper oxide nanoparticles synthesized chemically can vary depending on the specific type of copper oxide, the synthesis method used, and the surrounding environment.

Yes, the absorption coefficient of laser radiation by a material can depend on the beam polarization. This is because the absorption of light by a material depends on the orientation of the electric field with respect to the crystal lattice or molecular structure of the material. For example, in anisotropic materials, the absorption coefficient can be different for light polarized in different directions. In other materials, like many liquids and glasses, the absorption is isotropic and independent of polarization.

Jeong Bin Cho It would be very interesting to look at the distortion of the spectra. My last idea is to maximize the optical path, since the luminescence is non-directional, unlike the light absorption signal.

Joële Viallon Hello Joële, such a spectrum would definitely be useful for us.

Thanks!

Stefan