Photodissociation dynamics of CO2 at 157.6 nm by photofragment-translational spectroscopy

Publisher Website
Google Scholar
Abstract
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 β=2 for the O(3P) channel and β=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(v)+O(3P) channel was very broad (over 30 kcal/mol) and appeared to peak near CO(v=0). The value of β=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(ν2) 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(v=0)/CO(v=1)=1.9, for the CO(v)+O(1D) channel.