What is the difference between dephasing time of optical coherence and the relaxation time (depopulation time)? I think I know what a dephasing time is. Correct me if I am wrong. The dephasing time applies in stimulated Raman scattering when a coherent vibration of molecules is formed in the medium. So the vibration is modelled by an optical phonon. once the excitation pulse is off, the optical phonon vibration decays with a time constant (T2) which reflects the lifetime of optical phonon.
Now here is when I get confused: When the phonon decays and all the molecules are out of phase, is not this equivalent to relaxation of the excited vibrational state? I think about it this way: upon Raman transition, molecules will be in a higher vibrational excited state (say state with v=1). Now this state has a life time and molecules relax to the ground state after a certain life time. This process is of course spontanous.
So shouldn't dephasing time and depopulation time refer to the same thing?
Any explanation is highly appreciated!!!!
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