first of all, it looks like that the wavenumber axis in the plot is incorrect.
the broad feature may be fluorescence or elastically scattered light or a mixture of the two. what is your sample and what is the laser wavelength?
Dear Haghighi,
It appears that the detector is saturated around zero from -2000 to + 3500 (units not given). Ther easiest explanation would be a missing / wrong filter for Rayleigh (elastically) scatterered light.
Sometimes spectra looks like this if a wrong filter is in the beam pathway. Why the x axes is not correct, maybe the instrument is not right calibrated? Or the switch between higher resolution to lower (grating) was not done in a correct way. Which instrument are you using?
It seems that you missed a barrier filter in your setup for blocking the inducing laser.
Thank you all for your helpful comments.
The instrument is an AvaRaman spectrometer (Avantes, The Netherlands), wavelength: 532 nm
Sample: surface-engineered hybrid nanoliposomes loaded with polyphenolic compounds (10 mM)
The same problem kept resurfacing with spectra obtained from other samples (coating material, empty nanoliposomes and the polyphenol, separately)
This is my first experience with Raman spectroscopy, so I couldn’t locate the source of problem; is it hardware-related (filters, low wavelength of 532 compared to 785 and 1064, etc.), software-related (data processing procedures, smoothing, normalization, etc.) or sample-related (low concentration, intrinsic fluorescence, impurities, …)?
"wrong or missing filter", could you please expand on that?
recording spectra of a solid with such an instrument is tough for a first Raman experience. have you tried a simple liquid sample (e.g. alcohol or hydrocarbon either in a cuvette or directly through the glass wall of the bottle)?
the spectra you loaded up are a bit confusing: the numbers on the wavenumber axis do not make a lot of sense except the 0, where the laser line appears. there might be a filter missing, but it also seems strange to me that the spectrometer is aligned in a way that the laser wavelength is in the center as I don't assume that you are going to look at the (very weak) anti-Stokes branches.
Yep… actually I expected to observe peaks at about 600-800 cm-1 and 1500-1650 cm-1 to be able to interpret my samples’ identities and interactions but I cannot get that from these plots.
It seems as if the spectrum has flown away exactly where I need it!
as I mentioned in the previous message, I'd suggest to do a quick test with a known liquid to check the performance of the instrument. The interference from elastically scattered light should be substantially reduced in a clean liquid and the filter may sufficiently work in this case.
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