Vibrational temperatures and gain coefficient measurements by using spontaneous radiation data obtained in a shock driven CO 2—GDL

Abstract

A method for determination of vibrational temperatures in vibrationally-nonequilibrated CO 2—laser active medium for CO 2, CO and NO admixture molecules is developed and described in this article. The determination of vibrational temperatures of CO and NO molecules is based on spontaneous radiation intensity measurements in the 4.7 and 5.3 μm bands respectively and that of CO 2 molecules is based on the simultaneous measurement of radiation intensity in 4.3 and 2.7 μm bands. The CO 2 vibrational temperature measurements permitted restoration of the upper (00°1) and lower (10°0) laser levels populations and hence of the gain coefficient in (00°1–10°0) CO 2 laser transition. The vibrational temperatures of CO 2, CO and NO molecules in CO 2-GDL with the introduction of carbon monoxide or nitrogen monoxide instead of nitrogen in the chemically inert 0.1 CO 2 + 0.4N 2 + 0.5 He and reactive CO + N 2O + (N 2 + He) mixtures were measured. In these experiments the gain coefficient was measured by two independent methods: by probing laser technique and by restoration of the vibrational temperatures of CO 2. The values of gain coefficient and vibrational temperatures were also calculated numerically. This permitted to carry out a comprehensive study of population inversion generation in CO 2-GDL on inert and reactive mixtures with additions of CO and NO molecules.