Pulse photoacoustic technique for the study of vibrational relaxation in gases

Characteristic peculiarities of the formation of the photoacoustic-detector signal from excitation of absorbing gas molecules by a short laser pulse (τ(p) « τ(vt)) that allows for the natural oscillations of the microphone membrane are considered. A technique for τ(vt) measurement is proposed on the strength of the finding that the signal form is determined by the microphone membrane oscillation under low pressure (P ≤ 10 Torr). The results of measurement of the τ(vt) of the vibrational state ν(1) + 3ν(3) in H(2)O for the collisions H(2)O-(2)O and H(2)O-air are presented.