ABSOLUTE OSCILLATOR-STRENGTHS FOR PHOTOABSORPTION, PHOTOIONIZATION AND IONIC PHOTOFRAGMENTATION OF SULFUR-DIOXIDE .1. THE VALENCE SHELL

Absolute photoabsorption oscillator strenghts (cross sections) for the valence shell of sulphur dioxide have been measured using dipole (e, e) spectroscopy in the equivalent photon energy range 5-160 eV. Photoionization time-of-flight mass spectra have been collected using dipole (e, e + ion) coincidence spectroscopy from the first ionization potential up to 100 eV. Combination of the photoabsorption oscillator strengths with the photoionization efficiency and the ionic photofragmentation branching ratios determined from the mass spectra yielded partial oscillator strengths for the molecular and dissociative photoionization channels. The results are compared with previously published photoabsorption and photoionization data for SO2. Some deductions are made concerning the dipole induced breakdown pathways of SO2 under VUV energetic radiation.