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 molecules and of argon after excitation with tunable monochromatized synchrotron radiation that was scanned through the entire resonance region 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 fragmentation channels, including those comprising ionic and neutral fragments, have been determined. Implicitly we obtain also spectra of the total charge which are found to closely resemble each other and the photo-ion spectrum of atomic argon, thus reflecting analogous electronic processes in this atom and both molecules. Such processes are simultaneous or sequential double Auger ejection and photoelectron recapture via post-collision interaction. Branching among dissociation channels of equal total charge is similar for both molecules and generally varies little with photon energy, with a few notable exceptions at the pi* resonances and the ionization limits. Maximum kinetic energies of fragments are determined for purely ionic channels and compare well, as do the momentum correlations, with results of simulations based on a simple kinematical model. (C) 1997 Elsevier Science B.V.