Decay of and OCS after sulphur 1s photoexcitation: I. Total ionic charge spectra and electronic processes

Abstract

Deep core excitation of a small molecule leads to ejection of several electrons and dissociation into numerous alternative sets of fragment ions. We describe an experiment which identifies complete such sets arising from decay of triatomic molecules (and measures their total charge) via triply coincident detection in a time-of-flight mass spectrometer. Careful data correction furthermore enables estimation of contributions from channels comprising one neutral fragment. CS 2 and OCS molecules were photoexcited by monochromatic x-rays tuned through the entire region around the sulphur 1s threshold (2478 eV). For the first time energy dependent total photoion charge spectra were obtained for deep core excited molecules. They closely resemble those of argon at its K edge, demonstrating the similarity of electronic deexcitation. Electronic processes reflected in these spectra are ejection of excited valence or Rydberg electrons via shake-off and/or Auger decay, photoelectron recapture by post-collision interaction with a fast Auger electron, and pre-edge 1s ionization which extends to tens of eV below threshold. Results on the dissociative aspects are given in the following paper.

Dissociative Photoionization of Methoxycarbonylsulfenyl Chloride, CH3OC(O)SCl, Following Sulfur 2p, Chlorine 2p, and Oxygen 1s Excitations

“…35 For the triatomic species OCS and CS 2 , the ion yield spectra near the L and K absorption edges show definite transitions to the σ* orbitals. [43][44][45][46] Moreover, a slightly statespecific photofragmentation of carbonyl sulfide following sulfur 1s excitation has been observed as indicated by an atomic ion increment at the onset of the S 1s excitation. The cleavage of the carbon-sulfur bond is favored over the cleavage of the oxygen-carbon bond both above and below the sulfur 1s ionization threshold.…”

Decay of and OCS after sulphur 1s photoexcitation: II. Dissociation channels and kinematics

“…Branching ratios of dissociation channels, including those comprising a neutral fragment, have been determined for photon energies ranging from 2450-2800 eV. A thorough description of the experiment and data treatment is given in the accompanying paper (cf the preceding article in this issue (Esser et al 1997), henceforth referred to as I). Furthermore, total charge spectra of the dissociating molecular ion are presented there and discussed with respect to the information they provide on the electronic aspect of photodissociation, i.e.…”

Evidence for interatomic Coulombic decay in XeK-shell-vacancy decay of XeF2

“…The common hypothesis for deep inner-shell decay in a molecular environment is that of a localized cascade decay on the heavy atom accompanied by charge redistribution and Coulomb explosion [1,2,9,10]. Within this scenario, the same total final charge is produced in the cascade decay of an isolated heavy atom and in the decay of the same atom embedded in an environment.…”