Inner-shell excitation and fragmentation of sulfur aggregates

Abstract

Variable size sulfur aggregates (S-n with 3 less than or equal to n less than or equal to 8) were investigated in the S 2p excitation regime (160 eV less than or equal to E less than or equal to 175 eV) using monochromatic synchrotron radiation. Partial ion yields of mass-selected cations are compared with semiempirical extended Huckel calculations, yielding detailed information on the electronic and geometric structure of the aggregates. Inner-shell excitation in the S 2p regime leads to efficient formation of doubly charged species, which undergo rapid fragmentation via charge separation. The fragmentation pathways are investigated by photoelectron-photoion-photoion coincidence (PEPIPICO) spectroscopy. The charge separation mechanisms are interpreted in terms of Coulomb explosion. (C) 1999 Elsevier Science B.V. All rights reserved.