PHOTODISSOCIATION DYNAMICS OF CO2 AT 157.6 NM BY PHOTOFRAGMENT-TRANSLATIONAL SPECTROSCOPY

The photodissociation Of CO2 at 157 nm was studied by the photofragment-translational spectroscopy technique. Product time-of-flight spectra were recorded and center-of-mass translational energy distributions were determined. Two electronic channels were observed-one forming O(1D) and the other O(3P). With previously determined anisotropy parameters of beta = 2 for the O(3P) channel and beta = 0 for the O(1D) channel, an electronic branching ratio of 6% +/- 2%O(3P) was obtained, consistent with previous results. The translational energy distribution for the CO(upsilon) + O(3P) channel was very broad (over 30 kcal/mol) and appeared to peak near CO(upsilon = 0). The value of beta = 2 for the O(3P) channel was confirmed by comparing Doppler profiles, derived from our measured translational energy distribution, with previously measured Doppler profiles. This suggests that the O(3P) channel arises from a direct transition to an excited triplet state. The O(1D) channel had a structured time-of-flight which related to rovibrational distributions of the CO product. The influence of the excitation of the CO2(nu2) bending mode was investigated and shown to have a small but not negligible contribution. Based upon a comparison of our data with a previous vacuum-ultraviolet (VUV) laser induced fluorescence study, we obtain as our best estimate of the vibrational branching ratio, CO(upsilon = 0)/CO(upsilon = 1) = 1.9, for the CO(upsilon) + O(1D) channel.