Stimulated Raman scattering in the boundary region between impulsive and nonimpulsive excitation

Abstract

The generation mechanism of stimulated Raman scattering (SRS) in a gaseous medium pumped by a pulse with a duration close to one rotational period of molecular motion was studied. We found that the self-seeding effect caused by nonlinear pulse reshaping during propagation of a pump pulse was essential for the excitation of Raman coherence. This clearly explains the selective excitation of specific motions of molecules and the substantial reduction of the threshold of SRS generation.