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.