Hi Efi,

if these additional bands are sharp and random, these might be cosmic rays. These cosmic rays randomly hit your CCD detector. During point analysis, the spectrum is commonly captured in two or more accumulations, thus the correction will remove the cosmic rays because they only occur in one of the accumulations. During Raman imaging, spectra are commonly captured by one accumulation in order to reduce the time needed. Thus, the cosmic rays cannot be removed by comparing multiple spectra from the same location.

Dear Jan Schönig

Thank you very much for your reply.

These peaks are not sharp. I observed the peaks in 2 mixed samples (containing 3 kinds of materials).

When I measured the reference materials, two out of three spectra showed these 'ghost peaks', but was not observed in another.

Then, in order to evaluate the possible reasons, we need to see the spectra. Please explain a bit more detailed when you observe this feature (only during imaging?). The instrumental setup and experimental conditions would be helpful.

Dear Jan Schönig ,

Thank you again for your reply.

Yes, the ghost peaks only appeared in the imaging mode.

When I measured one of the constituent materials with different laser power:

0.1 mW and 0.02 mW, the one used the laser power of 0.02 mW, showed the lower peaks' height, but still are in the same positions.