Diode laser probing of vibrational, rotational, and translational excitation of CO2 following collisions with O(1D). I. Inelastic scattering

Abstract

Time domain diode laser absorption spectroscopy has been used to measure state-specific energy deposition in the vibrational, rotational, and translational degrees of freedom of CO2 following the 248 nm photolysis of ozone in a low pressure mixture of CO2, O3, and O2. Nascent rotational population distributions have been measured in a number of low-lying CO2 vibrational levels, including 0000, 0110, 0220, 0200, 0330, 1000, and 0001. In addition, measurements of CO2 translational excitation have been obtained for the majority of the rovibrational states which were probed. The results suggest that the prompt absorption signals observed so far arise from inelastic scattering between CO2 and the translationally hot O(1D) and O2(1Δ) photofragments rather than electronic quenching of O(1D) to O(3P) by collisions with CO2. Simple calculations indicate that the latter process should provide substantially more CO2 rotational and translational excitation than is observed here.