Vol. 37, issue 10, article # 1

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 t_VT. 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.

Keywords:

gas analysis, laser pulse duration, photoacoustic signal, molecular absorption, VT relaxation, CO2 laser

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