Stepwise dependence of a portion of hot molecules on the intensity of exciting radiation

A theoretical analysis is presented of the coherent mechanism for the formation of the nonequilibrium energy distribution of polyatomic molecules in an infrared laser radiation field. It is shown that the physical cause for the separation of molecules into cold and hot ensembles is the interference of alternative channels of the excitation of zones of energy levels. A dependence of a portion of the hot molecules on the intensity of laser radiation is obtained. In the case of decreasing dipole moments of the interfering transitions, this dependence has a step-wise increasing character. In certain conditions, a coherent capture of a portion of the molecules in the initial state can occur. Theoretical results are compared with experimental data obtained for OsO4 molecules.