Kinetic spectroscopy of highly excited states of polyatomic molecules 1. Wave properties of transformation of population distribution under pulse excitation

The properties of a set of macrokinetic equations governing population of excited states of polyatomic molecules under pulse excitation are analyzed. The generalized master kinetic equation (MKE) is derived for the dimensionless population distribution function with due regard for the sources and sinks of excited states. At energies E exceeding the mean thermal energy, the solution of the generalized MKE assumes the form of a travelling front of a population wave. In the frame of reference tied to the moving front of a population wave, the solution has the form of an exponential energy distribution of populations with the characteristic variation range directly related to Delta E. Away from the sources and sinks of excited states and at E much greater than Delta E, the population front velocity is constant and obeys a simple relaxation equation.