Hi, I'm recently working with DRIFT-IR spectrometer and I'm having some problems with my spectra. I have noticed that there are some peaks at 3000~2800 cm-1 that appear in all single beam spectra(as in the picture). Those peaks keep present in all spectra( even when we try collecting pure KBr spectra).
Can anyone please tell me what are those peaks? and how they affect the spectra? Thank you
P/S: We are using DRIFT-IR system with environmental chambers(ZnSe windows) and our experiments include collecting spectra during sample thermal treatment in the environmental chambers
These are the asymmetric C-H stretching vibration (2918 cm-1) and the symmetric C-H stretching vibration (2853 cm-1) of the CH2-group. The shoulder at the high-wavenumber side of the asymmetric stretching vibration belongs to the CH3-group. Probably machine-oil...
Thanks so much for your answer, Mr. Thomas Mayerhöfer. May I ask just a small extra question: Do those peaks normally appear in case of DRIFT-IR? and how may I eliminate them from my spectra?
Again, Thank you very much.
The effect of temperature must also be considered depending how high you increase it. This could favour oil vaporization in the chamber. Check if this contamination is somehow T dependent.
As most have said you have hydrocarbons on windows or mirrors. They may subtract if you have a reference spectrum to subtract from your sample spectrum you will be fine...if you don't need the hydrocarbon region. Otherwise, time to clean!
In case of someone still have this problem, these 3 peaks with this configuration could be attributed to the use of scouring cream (probably during the cleaning of the mortar).
I asked this question about 30 years ago. I was told these peaks were due to epoxy resin used to anchor the detector to it's mounting plate. Whether that is correct or not - who's to know? But these peaks are small and should ratio out without issue as they are part of the single beam spectrum.
These peaks are omnipresent - the only IR spectra I ever saw without them did not cover the range... ;-)
These are very common artefacts. Finger oil also can produce them or an oily/greasy film residue on cleaning cloths. Alcohol/acetone is an effective means to remove surface contamination however if the cleaning cloth is contaminated, then the surface contamination will just be re-introduced.
Other sources include hydrocarbons in floor waxes and other cleaning products. They get in the air and over time, even with a vacuum or N2 purged bench they will form a film on your optics. Requires cleaning of mirrors in the interferometer. This is often just subtracted unless the application doesn't allow background subtraction.
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