Hi,
We have a UV-VIS spectrophotometer in our lab. The measurement it gives is basically extinction. I am interested in measuring absorption and scattering separately instead of extinction of my samples. How is it possible?
Dear researcher,
Please consider the absorption formula:
I(x)=I0*exp(-alpha*x)
where alpha is the absorption coefficient and I and I0 are light intensity at distance x and source respectively. Using extinction of light for different values of x, one can determine the absorption coefficient for any sample.
What is your sample? Lot depends on it. This separation is possible with proper choice of the sample and measurement geometry.
In collinear geometry, one measures extinction due to absorption of photons or extinction due to scattering.
If you choose a sample with chromophores which do not absorb in the particular region of electromagnetic spectrum then one measures only reduction in intensity due to scattering.
For absorbance measurements, you will need a sample with chromophores which absorb photons in that particular region of the electromagnetic spectrum.
If you want to measure scattering only, then collinear geometry (which is generally present in all spectrophotometers) will not help. You will need a right angled geometry or some other geometry.
Scattered light will have the same wavelength as that of the incident light. If one changes the wavelength of incident light then the scattered light wavelength also changes.
There is also Raman scattering from the sample which occurs at a wavelength which is 3500 cm-1 red shifted from the excitation wavelength. This is generally weak and is important in non-collinear geometries.
If your samples are thin films then you could get the desired information applying Kubelka-Munk theory.
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