IONIZATION AND FRAGMENTATION OF OCS AND CS2 AFTER PHOTOEXCITATION AROUND THE SULFUR 2P EDGE

Photo-ion time-of-flight mass spectra have been taken of OCS and CS2 m olecules and of argon after excitation with tunable monochromatized sy nchrotron radiation that was scanned through the entire resonance regi on of the sulfur (or argon) 2p absorption. Flight times of up to three charged fragments were measured in coincidence. By means of a careful data reduction branching ratios of the molecules for numerous fragmen tation channels, including those comprising ionic and neutral fragment s, have been determined. Implicitly we obtain also spectra of the tota l charge which are found to closely resemble each other and the photo- ion spectrum of atomic argon, thus reflecting analogous electronic pro cesses in this atom and both molecules. Such processes are simultaneou s or sequential double Auger ejection and photoelectron recapture via post-collision interaction. Branching among dissociation channels of e qual total charge is similar for both molecules and generally varies l ittle with photon energy, with a few notable exceptions at the pi res onances and the ionization limits. Maximum kinetic energies of fragmen ts are determined for purely ionic channels and compare well, as do th e momentum correlations, with results of simulations based on a simple kinematical model. (C) 1997 Elsevier Science B.V.