METHOD FOR THE STUDY OF FAST VIBRATIONAL RELAXATION OF MOLECULES USING SPECTROPHONE

A technique for measuring the vibration translational relaxation time of molecular gases using the spectrophone is described. The technique is based on the measurement of the phase of natural oscillations of the microphone membrane as a function of pressure of the gas under study. These oscillations manifest themselves in a shape of the optoacoustic (OA) signal at low gas pressure in the OA cell when the absorbing molecules are excited by short laser pulses. As an example the results on the relaxation time of the v1+3v3 state of H2O molecule in H2O-H2O and H2O-air collisions obtained using the OA cell of various sizes are presented.