Theory of the time and frequency dependence of near-resonant raman scattering and quantum beats

A calculation of the time dependence of light scattering from an atom or molecules yields a continuous transition from fast Raman scattering to resonance fluorescence in agreement with recent experiments. If the resonant excited state has two or more nearby levels, “quantum beats” may be observed. These quantum beats are present even if the incident light is tuned off resonance.