What do peaks mean in a Raman spectroscopy intensity vs wave number graph?

[mkbh_10]

Tell me what do the peaks in the graph show which is b/w Intensity and wave number in raman spectroscopy ?

Are the peaks due to transition from a grnd state to an exicted state or vice versa , low energy are stokes and high energy are the anti stokes one

 

[mkbh_10]

will any1 reply

 

[Claude Bile]

The peaks are due to Raman-active transitions in the vibrational energy states; that is, transitions where there is a variation in the polarisability of the molecule. The peaks are the pump wavelength plus/minus the energy of the vibrational transition for anti-stokes/stokes lines.

For example, if I illuminate the sample with 442 nm radiation, the Raman signal is detected around (say) 460 nm. The difference in energy between the 442 and 460 nm photons is the energy of the vibrational transition.

Claude.