Dear Rekha, maybe I can help you, but you should spend a few more words about your experimental setup. For example, are you dealing with a thin film deposited onto a substrate? In affirmative case, which kind of substrate is it? How thin is this film, a few microns or a few nanometres? Which range of wavelengths are you working with, visible, UV or X-rays? Are you working in grazing or normal geometry? Is the film thickness meant to be constant or variable from point to point?

@ Daniele Spiga The substrate is ITO and film is CdS on it.the film is a few nanometers(but not exactly measured).I am working with wavelength range 300-800nm in UV/Vis.the film thickness is constt point to point.....

Ok, since the thickness is constant, there are good codes you can use to interpret your interference diagram. I always use IMD to interpret my measurements in X-rays: you can find it at http://www.rxollc.com/idl/ - but it requires you to run it in a IDL environment. Moreover, it requires reliable optical constants of ITO, which is not present in the IMD database. Do you have them at hand?

Hi Rekha, a very good general reference for the X-ray interactions with matter are the Henke tables. The data is accessible on the Center for X-ray Optics (CXRO) site out of Berkeley Labs. On the following link, you can look up the attenuation length, which of course is the inverse of the absorption coefficient, as a function of the X-ray energy:

http://henke.lbl.gov/optical_constants/

You could also use "mucal" to calculate the absorption coeffients:

http://www.csrri.iit.edu/mucal.html

You do have to be careful about the densities you use. Mucal concerns itself with atomic absorption of the elements in their common form, and so for oxygen I believe they use the density of oxygen gas. the CXRO site allows you to input the density, which is a big help.

If you have more specific questions, please feel free to contact me.

Dear Faisal, I am afraid that Rekha is not using X-rays. Probably some information in a range extended to the visible range is provided by Palik:

Handbook of Optical Constants of Solids', Ed. by Edward D. Palik, Academic Press, Inc., 1985.

But I do not know still if materials like ITO are included.

Hope this helps.

Daniele, you are right (as I now see from her followup clarification). The resources I pointed to do not are not very useful below 10 eV photons.

Dear Rekha,

You may find some useful information in the attached paper.

Paper

How do I do this for a super-lattice MBE epitaxial film?

https://www.researchgate.net/post/X-ray_Rocking_Curve_Analysis_of_Super-lattice_SL_Epitaxial_Structures_What_are_some_of_your_practical_experiences_with_this_method

Appreciate any help! Thanks!

Rekha, I am afraid, there is no way you can find abs. coefficient from absorbance without the value of thickness. You can use T or A or T and R, but value of thickness is an essential parameter. You may try to find 't' by some othher technique like surface profilometer or optical profilometer or cross-sectional FESEM or TEM. Good luck!