Kinetic energies and angular distributions of oxygen atom photofragments produced by photodissociation of O2 and N2O in the vacuum ultraviolet

Abstract

A gas phase chemi‐ionization process is used to detect O atoms produced by photodissociation of O₂ and N₂O. For the photon energies used here the accessible O atom states are within the ground ³P levels and the metastable ¹D and ¹S levels. Kinetic energies of the O atom photofragments are determined using an atomic beam time‐of‐flight technique, and the O atom angular distributions are determined by varying the angle between the direction of the photon beam and the atomic beam flight path. Dissociative transitions within the Schumman–Runge continuum of O₂ and the principal vacuum ultraviolet absorption continuum of N₂O yield results in agreement with previous predictions. For the dissociation of O₂ at wavelengths of 120 and 124 nm, the principal dissociation products are O(³P)+O(¹D); and, at these wavelengths, the O atom angular distribution is consistent with previous conclusions that predissociation is important. Using existing theories of photofragment angular distributions, an asymmetry parameter having a value of (−0.61±0.05) is obtained for predissociation in O₂ at the 10.0 and 10.3 eV absorption features.