Theory and application of time-resolved optoacoustics in gases.

The acoustic waves generated by a relaxing gas have a shape which depends on the ratio of the relaxation rate to the acoustic propagation rate. It is shown how the relaxation time constant can be extracted from this waveform for a variety of relaxation rate laws, using a Green’s function to solve the linearized wave equation. The accuracy of the method is confirmed by measuring the relaxation rate constants for OCS diluted in Ar and He. These, plus a previous measurement of the relaxation rates of highly excited SF6 and C6F5H in Ar, are in good agreement with the literature. [ABSTRACT FROM AUTHOR]