Hello, I am currently in an analytical chemistry course where I am required to write a report on Raman Spectroscopy. The typical description of Raman Spectroscopy is the excitation of an electron to a "virtual" state, whereupon it can relax to a non zero vibrational level in its ground transitional state and scatter light of a correspondingly different frequency. The difference in the frequencies of the incident and scattered light account for the "Raman Shifts" of a molecule, which can be organized into a spectrum according to wavenumber. My instructor has informed that this definition is wrong, and that this "virtual" state does not exist. I am trying to find the real way Raman Spectroscopy works, with little success. I have checked a few journal articles and a couple of books, as well as numerous websites. Most provide the traditional description. Some have referenced the polarization of the light changing and interaction with phonons, but do not explain specifically how such interactions can cause a change in the polarization, or how a change in polarization relates to a change in frequency (aka Raman Shift) to generate a spectrum. At least, I have failed to understand the relationship. Is anyone here able to provide some insight into how Raman really works, then? Or at least clarify this relationship between phonons, changes in polarization of light, and changes in the frequency of light? References to appropriate sources or direct explanations are equally appreciated! Thank you very much for your time!