I have thin film samples whose composition is known. When samples were sent for Raman Spectroscopy, operator is for the asking scan range. How do I decide it?
are you sure? or did he ask about the frequency of the Laser? Apart from that where are the characteristic vibrancy of your sample?
I presume that he wants to know the expected positions of the Raman lines based on your known composition. This reduces the scan range and the time it needs to scan. For example, the Raman shift of Si is 520 nm, so he can scan from 460 to 540 cm-1 instead of scanning the full range. If you tell him the sample composition, he should know what range to scan. On the other hand, you might have a preference for details of a specific bond and maybe want to limit to this one bond?
You have 2 choices. 1) Accept what has been presented in the literature previously and stay within that range. Usually 5-1000 cm-1 for solid state materials, other ranges depending on the material composition. 2) ignore the literature and scan the entire spectrum available to the instrument with large step size (2-5 cm-1) to see what exists. Repeat with smaller step sizes to gain detail of particular peaks. If you do this at low temperature (80K or lower) you will pick up the fluorescence peaks and the measurement should be repeated with at least 2 excitation frequencies to distinquish Raman from Fluorescence. I highly recommend option 2. Also, I am assuming a Czery-Turner scanning type spectrometer, if your operator is using a CCD camera variant, then use your best judgement on what range is available for the time/cost to scan.
One can get a rough estimate from the type of sample, the best way to go about it if one has a rough idea of the sample refer to the literature and set the scanning range.
Also the number of acquisitions can be set to get better results if one is interested in a particular peak.
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