Vibrational energy transfers in ozone from infrared double-resonance measurements

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Abstract
Vibrational energy transfer processes in pure ozone have been studied by means of a time-resolved infrared double-resonance technique using two CO2 lasers. The intermode transfer between the Coriolis-coupled ν1 and ν3 modes has been observed for the first time and its rate constant measured. The near-resonant vibrational energy transfer populating the ν2+ν3 state has been also directly observed, as well as the vibrational deexcitation of the ν1 and ν3 states including the transfer process to the ν2 mode and the direct V-T,R processes. From a kinetic analysis of the vibrational relaxation, a numerical model was formulated allowing by comparison to the experiments to determine the rate coefficients for the processes. A rate coefficient of 2.4×106 s−1 Torr−1 was obtained for the intermode transfer between the Coriolis coupled ν1 and ν3 modes. Also a rate coefficient of 7×105 s−1 Torr−1 was derived for the process populating the ν2+ν3 state. The rate coefficient corresponding to the intermode transfer from ν1 and ν3 to ν2 was found to be (2800±500) s−1 Torr−1, a value clearly smaller than that obtained in previous studies. Finally the direct deexcitation from the ν1 and ν3 states, not taken into account in previous works, was found to be rather efficient, its rate coefficient being not negligible (∼600 s−1 Torr−1) as compared to the deexcitation coefficient from the ν2 state which was found equal to (2250±300) s−1 Torr−1.

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