Deactivation of the molecular oscillations of carbon dioxide in a stream which is cooled

The paper presents experimental results on the relaxation of the molecular oscillations of carbon dioxide which is cooled upon flowing out of a plane nozzle located in a shock tube. The initial pressure range of the gas was 3-10.5 atmospheric pressures and the initial temperature range was 870-2470 K. The gas was irradiated with 10.6-micron radiation from a CO2 laser. It was shown that the absorption coefficient (with respect to the laser radiation) of the gas was very weakly sensitive to variations in the probability of Q-23 vibrational energy exchange between the second and third types of molecular oscillations of CO2. The role of anharmonicity and other factors which lead to a distinction among the kinetic characteristics of vibrational relaxation during the heating and cooling of CO2 at temperatures between 600 and 1400 is judged to be insignificant.