Inner-shell excitation and fragmentation of sulfur aggregates

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