Theoretical and experimental investigations of I.R. radiation transfer in vibrationally nonequilibrated molecular gas containing CO 2 and CO

Abstract

Radiation intensity and emissivity of the 4.3 and 2.7 μm vibrational- rotational bands of carbon dioxide and of the 4.7 μm band of carbon monoxide have been numerically calculated and experimentally measured over a wide range of parameters of vibrationally nonequilibrium mixtures expanding through the supersonic nozzle of a gasdynamic CO 2 laser. Theoretical determination of radiation characteristics of the active CO 2 laser medium in the i.r. spectral region, averaged over the rotational structure, has been made by means of the vibrational- rotational band theory using nonequilibrium energy distributions of molecules over vibrational levels reconstructed on the basis of calculations of vibrational relaxation kinetics in the mixture. A study has been carried out of the effect made on the spectral and integral radiation and absorption of the CO 2 and CO bands under consideration by the introduction into the CO 2 + N 2 mixture of water molecules, essentially accelerating the processes of V- T relaxation and by the substitution of carbon monoxide for nitrogen in the CO 2 + N 2 + He mixture leading to the alteration of the intermolecular V- V exchange course. The conditions under which radiation intensity or emissivity measurements make it possible to realize reliable diagnostics of vibrational-translational and vibrational-vibrational relaxation processes occurring in a gasdynamic active laser medium have been determined.