Dipole (e,e plus 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)

The branching ratios for molecular and dissociative photoionization of carb onyl sulfide (OCS) in the valence shell continuum regions and the inner she ll (S 2p, 2s and C 1s) regions have been determined using dipole (e,e+ ion) coincidence spectroscopy (similar to 1 eV FWHM) at equivalent photon energ ies from the first ionization threshold up to 300 eV. The absolute partial oscillator strengths for molecular and dissociative photoionization have al so been determined from recently published absolute photoabsorption oscilla tor strength data (R. Feng, G. Cooper, C.E. Brion, Chem. Phys. 252 (2000) 3 59) together with photoionization branching ratios and the (multi-dissociat ive-corrected) photoionization efficiency obtained from time-of-flight mass spectra reported in this work. The doubly charged molecular ion (OCS2+) an d its dissociation products (mainly OC+, S+, O+ and C+) have also been stud ied in this work. Much higher relative abundances of these products have be en found above the S 2p ionization edge (170.72 eV), which is due to Auger processes combined with Coulomb explosion. The presently reported results h ave been compared with previously published data where possible. (C) 2000 P ublished by Elsevier Science B.V. FLU rights reserved.