Resonance Raman four‐wave mixing in molecular systems

Abstract Non‐linear vibronic spectra of molecules in solution were considered. Probe profiles (PP) of CARS with three laser frequencies, treated as Raman four‐wave mixing (Raman FWM), were calculated and compared with excitation profiles (EP) of CARS and of spontaneous Raman scattering. It is demonstrated that the PP of Raman FWM is a characteristic that can be used instead of the EP of spontaneous Raman scattering. The dependence of the lineshape for Raman FWM was modelled. The advantages of Raman FWM are mentioned. In contrast to CARS with two lasers, it is easy to penetrate the high‐wavenumber side of the vibronic spectra and to avoid a significant absorption at the exciting wavenumbers.