I guess it is fluorescence (880 nm) from one of the inorganic dopants, but what is it?
First thing to do : chnage the excitaiton wavelength, if the band is still there AND at thes ame position it is a Raman band
At 1400 cm-1 you are close to C=O stretch , could come from any organic pollution of the slide (try to clean and no not touch with hands)
if not then it is fluorescence but at 880 nm it sounds very strange....
Calcium-bearing minerals fluoresce around 1400 cm-1 in 785 nm excitation. If you use another wavelength that fluorescence mode disappears, yes? To be honest, I'm not sure if it is calcium or something that replaces calcium, but all calcium-bearing minerals seem to have that mode.
At 785nm, glass emits a fluorescence spectrum. Thus the spectra recorded in glass vials may show a large back- ground around 1400cm-1 due to the glass being close to the focal volume. (http://www.horiba.com/fileadmin/uploads/Scientific/Documents/Raman/RA19.pdf)
Typically the Si from the glass in the slide; there is a combinational phonon mode around ~1400 cm-1.
The band is not coming from pollution or any organics. The band is fluorescence. It disappears at other wavelengths such as 535 or 638 nm. The phenomenon is actually quite known and published, but the reason is not. I was trying to measure fluorescence/phosphorescence using a fluorometer (I have many detectors sensitive in this region), but did not see much.
Is it really desappears at 535 or 633-nm excitation? In my experiments this fluorescence band is still exist at about 880 nm, but it corresponds to much larger Stokes Raman shift.
As others have said there are several possible contributions from the glass slide. If you need to use the slide in transmission mode I'd suggest switching to a quartz slide. If you can get by in reflectance cover your slide in a peice of aluminium foil fixed with double sided tape.
Looks like a signal from either Ca or Na oxides (microscopy slides are usually made from soda-lime glass); quartz has more levelled spectrum at 785 nm ex, without the broad peaks at 1400 and 1900 cm-1.
- Badges
- Science topic