Time-Dependent Analysis of Population Inversions in an Expanding Gas

A time-dependent technique for the numerical solution of convergent-divergent, nonequilibrium nozzle flows has been used to analyze the rapid, vibrational nonequilibrium, supersonic expansion of a mixture of CO2, N2, and H2O, wherein the finite rate molecular energy transfer processes can result in a population inversion between the (001) and (100) vibrational energy levels of CO2. Results for such population inversions are presented. Among these, a comparison has been made between the present results and the recent results of Basov et al.; this comparison indicates that Basov's calculations overestimate the population inversion in an expanding mixture of CO2 and N2. In addition, results are presented from a series of numerical experiments conducted to assess the validity of several simplified methods for computing population inversions.