Can Molar Absorptivity Values Be Calculated Without Experimentation?

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In summary, there is no one-size-fits-all answer to this question. Different substances will have different microwave spectra, and it may be difficult to calculate them without doing some experimentation.
  • #1
sid_galt
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Is there a way of calculating molar absorptivity values of various substances without resorting to experimentation?
 
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  • #2
To ascertain a molar absorptivity under certain conditions (for accurate quantitative analysis) you'll need to do some experimentation with standards, that is don't ever assume a molar absorptivity value for quantitative analysis. Molar absorptivity is pretty complex and involves many factors (e.g. orientation of the chromophore and quantum characteristics), I'm not aware of any current measures for an all around method for theoretical molar absorptivity calculations (that is for any substance). Although I suppose it's possible for compounds of a limited complexity, especially for atomic values.
 
  • #3
Thank you for the reply.

Any place (books, websites) where I can find data on the microwave spectra of compounds like water, hydrogen peroxide, carbon monoxide, hydroxide ion, etc.
 
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  • #5
Thank you for the reply. The problem is that I will probably need a way to calculate the microwave spectra of the various species as I am working with multiple temperatures from 500K to 2000K.

I have found the rigid rotor model for rotational energy. Is there a way to relate the energy of the system with the temperature?
 
  • #6
Perhaps then one should look for microwave emission spectrum.

I think the paper (RAdiScienceCol.pdf) goes into some detail, but I only browsed it.

At the temperatures, particularly 2000K, it would seem emission is the main effect.

I found this - http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JPCRBU000007000001000311000001&idtype=cvips&gifs=yes [Broken]
but it must be purchased, and it is not clear from the abstract if it includes the temperature range of interest.

If found this string - "Microwave Spectra of Molecules of Astrophysical Interest" about midway down the NIST page - http://srdata.nist.gov/gateway/gateway?keyword=spectrum
That led me to the article above.

Perhaps you could contact the various authors.
 
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  • #7
Emission would occur due to Blackbody Radiation right?
 

What is absorptivity?

Absorptivity is a measure of how much light or other electromagnetic radiation is absorbed by a material. It is a dimensionless quantity and is usually expressed as a percentage or decimal fraction.

How is absorptivity calculated?

Absorptivity is calculated by dividing the amount of light or radiation absorbed by the material by the amount of light or radiation incident on the material. This can be expressed mathematically as A = (I0 - It) / I0, where A is the absorptivity, I0 is the incident intensity, and It is the transmitted intensity.

What is the difference between absorptivity and absorbance?

Absorptivity and absorbance are related but different quantities. Absorptivity is a measure of how much light is absorbed by a material, while absorbance is a logarithmic transformation of absorptivity and is used to quantify the amount of light that is absorbed by a material. The relationship between the two is given by A = log10(1/Absorptivity).

How does temperature affect absorptivity?

The absorptivity of a material can be affected by temperature in several ways. The material's physical and chemical properties may change at different temperatures, leading to changes in its ability to absorb light. Additionally, temperature can also affect the wavelength of light that is absorbed, which can impact the overall absorptivity of the material.

What is the significance of absorptivity in scientific research?

Absorptivity is an important parameter in many scientific fields, including chemistry, physics, and materials science. It is used to characterize the properties of materials, such as their ability to absorb light or other forms of radiation. This information can be used to understand the behavior of materials, develop new products, and improve existing technologies.

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