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Re^3: Transformation Firefly IR intensities to material property values (e. g. like absorption coefficient in 1/cm or 1/(cm*mol))

Alexey A. Popov
alxy.popov@gmail.com

Dear Thomas,

unless you have experimentally determined absolute values of absorption (which means that you know optical path, concentration, beam square, etc), the play with absolute values from computations makes little sense. A standard way to compare experimental and computed IR spectra is simply applying an arbitrary uniform peak width, usually something like 2-4 cm-1, but you may adjust this value simply by choosing something that fits your experimental data better. And since nobody's usually working with absolute intensities, visualization packages you mentioned usually give the data in relative values (say, by normalizing to the highest intensity peak).

If you are still interested in the absolute values, then you can get a relation between the area and the value at the peak maximum simply from the properties of the functions (Gaussian, Lorentzian, etc) you use to approximate your peaks.

Say, for a Gaussian function y = A*exp{-(x-b)^2/2c^2}, area is A*c*(2*pi)^0.5

All the best,
Alexey

On Wed Jul 27 '11 0:13am, Thomas H. wrote
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>Dear Alex,