S 2p excitation and fragmentation of sulfur aggregates

Synchrotron radiation from the storage ring BESSY-I is used to excite the S 2p regime (150–190 eV) of sulfur aggregates Sn, n=2–8. Valence states are identified in photoion yield spectra of mass selected Sn+ cations in combination with extended Hückel calculations. Mass spectra, partial ion yields, and photoelectron–photoion–photoion (PEPIPICO) coincidence spectra are reported, yielding a consistent picture of massive decay processes occurring in the S 2p regime. PEPIPICO spectra especially give detailed information on the fragmentation mechanisms of doubly charged aggregates. It is shown that most cation pairs are formed via charge separation originating from S8++. We derive values for the kinetic energy releases in multistep fragmentations assuming that charge separation is driven by Coulomb explosion.