Kinetic Cooling of a Gas by Absorption of CO2 Laser Radiation

Abstract
The effect of kinetic cooling due to the absorption of 10.6-μ CO2 laser radiation in the atmosphere has recently been predicted. In this letter, experimental evidence for this effect is presented. Transient-density increases due to the kinetic cooling have been observed in CO2–N2 mixtures following the propagation of an ∼ 1-μsec 0.5-J CO2 laser pulse through the gas. The experiments were performed with varying concentrations of CO2 and the observed cooling and subsequent heating effects are explained using the usual three-level approximation for vibrational-energy transfer in CO2–N2, together with known relaxation rates.

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