Infrared radiation generation at forced combination scattering

Equations describing the generation of medium-wave and long-wave infrared radiation in SRS are obtained in the situation when the frequency of the first or second Stokes components is smaller than the vibration frequency excited by the SRS process. It is shown that such generation occurs due to two-photon emission and four-photon parametric emission. In many cases, these equations make it possible to relatively simple estimate the efficiency of such generation of IR radiation.