Dipole (e,e+ ion) coincidence studies of the ionic photofragmentation and photoionization of carbonyl sulfide in the valence shell and S 2p, 2s and C 1s inner shell regions (10–300 eV) Original Research Article

The branching ratios for molecular and dissociative photoionization of carbonyl sulfide (OCS) in the valence shell continuum regions and the inner shell (S 2p, 2s and C 1s) regions have been determined using dipole (e,e+ ion) coincidence spectroscopy (∼1 eV FWHM) at equivalent photon energies from the first ionization threshold up to 300 eV. The absolute partial oscillator strengths for molecular and dissociative photoionization have also been determined from recently published absolute photoabsorption oscillator strength data (R. Feng, G. Cooper, C.E. Brion, Chem. Phys. 252 (2000) 359) together with photoionization branching ratios and the (multi-dissociative-corrected) photoionization efficiency obtained from time-of-flight mass spectra reported in this work. The doubly charged molecular ion (OCS2+) and its dissociation products (mainly OC+, S+, O+ and C+) have also been studied in this work. Much higher relative abundances of these products have been found above the S 2p ionization edge (170.72 eV), which is due to Auger processes combined with Coulomb explosion. The presently reported results have been compared with previously published data where possible.