Photodissociation of Ozone from 321 to 329 nm: The Relative Yields of O(³P₂) with O₂(<i>X</i> ³Σ_g^–), O₂(<i>a</i> ¹Δ_g) and O₂(<i>b</i> ¹Σ_g⁺)

Abstract

Product imaging of O­(³P₂) following dissociation of ozone has been used to determine the relative yields of the product channels O­(³P₂) + O₂(<i>X</i> ³Σ_g^–) of ozone. All three channels are prominent at all wavelengths investigated. O₂ vibrational distributions for each channel and each wavelength are also estimated assuming Boltzmann rotational distributions. Averaged over wavelength in the measured range, the yields of the O­(³P₂) + O₂(<i>X</i> ³Σ_g^–), O­(³P₂) + O₂(<i>a</i> ¹Δ_g), and O­(³P₂) + O₂(<i>b</i> ¹Σ_g⁺) channels are 0.36, 0.31,and 0.34, respectively. Photofragment distributions in the spin-allowed channel O­(³P) + O₂(<i>X</i> ³Σ_g^–) are compared with the results of quantum mechanical calculations on the vibronically coupled PESs of the singlet states B (optically bright) and R (repulsive). The experiments suggest that considerably more vibrational excitation and less rotational excitation occur than predicted by the quantum calculations. The rotational distributions, adjusted to fit the experimental images, suggest that the dissociation takes place from a more linear configuration than the Franck–Condon bending angle of 117°. The dissociation at most wavelengths results in a positive value of the anisotropy parameter, β, both in the experiment and in the calculations. Calculations indicate that both nonadiabatic transitions and intersystem crossings substantially reduce β below the nominal value of 2