Kinetics of heat release at absorption of laser pulse by binary mixture of molecular gases with different vibrational-translational relaxation times
O.Yu. Nikiforova, Yu.N. Ponomarev
V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
Keywords: gas analysis, laser pulse duration, photoacoustic signal, molecular absorption, VT relaxation, CO2 laser
Abstract
The photoacoustic (PA) method is widely used in studies of the absorption of optical radiation by various media. As a rule, it is assumed that the PA signal is formed due to the relaxation of vibrationally excited molecules with a common characteristic time τVT. The kinetics of heat release in a PA cell at absorption of a laser radiation pulse in a mixture of two molecular gases with two independent channels of vibrational-translational relaxation with very different times is considered. An example of calculations of the kinetics of heat release for a mixture of H2O and CO2 at absorption of a CO2 laser radiation pulse and variations in gas concentrations is presented. It is shown that it is necessary to take into account the relationship between the laser pulse duration and the characteristic times of vibrational-translational relaxation in the gas mixture under study.
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