Effect of stimulated emission on the distribution of CO molecules over vibrational levels

The vibrational distribution function (VDF) of CO molecules is measured in the presence and absence of generation in a CO laser pumped by a longitudinal dc discharge. Kinetic equations for the VDF and the Boltzmann equation for the energy distribution function of electrons are solved simultaneously in a theoretical model. A comparison of the experimental and calculated lasing spectra and VDF demonstrates their good agreement. By introducing an absorbing cell with different gases (NO, C₂H₄, CO₂, C₆H₆) into a resonator, the influence of selection of laser lines on the lasing spectrum and the VDF of CO molecules is studied. It is shown experimentally that the population of CO molecules at vibrational levels involved in lasing and at higher levels strongly decreases and the VDF at lower levels changes insignificantly. It is demonstrated that the VDF shape of CO molecules at high vibrational levels can be changed by introducing intracavity absorption.