Sulfur 1s excitation of S-2 and S-8: Core-valence- and valence-valence-exchange interaction and geometry-specific transitions

Abstract

Sulfur 1s excitation of S-2 and S-8 is reported. The experiments made use of monochromatic synchrotron radiation from the BW-1 beam line at the HASYLAB (Hamburg, Germany), where total cation yields and photoionization mass spectra were investigated as a function of the source temperature that was used for evaporation of alpha-sulfur. The near-edge structure undergoes characteristic changes as a function of the source temperature, reflecting significant size- and geometry-dependent changes in electronic structure of the sulfur clusters. The detailed analysis of the near-edge features is obtained from ab initio (MR-SDCI) calculations that focus on S-8 and S-2. The present results are discussed in comparison to previous work on inner-shell excited sulfur clusters as well as condensed sulfur. The near-edge structure of S-2 is compared to that of O-2 and Se-2, yielding characteristic differences in core-valence and valence-valence-exchange interaction. (C) 2002 American Institute of Physics.