DISSOCIATIVE MULTIPLE IONIZATION FOLLOWING VALENCE, BR(3D), AND SI(2P) INNER-SHELL PHOTOEXCITATION OF SIBR4 IN THE RANGE OF 30-133 EV

The photoionization of SiBr4 in the valence shell, and the Br(3d) and Si(2p) inner shell excitation/ionization regions, has been studied by using a time-of-flight mass spectrometer and synchrotron radiation ove r the range 30-133 eV. The photoionization efficiency curve of SiBr4 h as been recorded as a function of the incident photon energy. Dissocia tion processes of SiBr4 have also been investigated by photoelectron-p hotoion coincidence and photoion-photoion coincidence (PIPICO) techniq ues. Various monocations of Br-n(+) (n = 1, 2) and SiBrn+ (n = 0-4) ar e detected along with dications of Br2+ and SiBrn2+ (n = 0, 1, 3) in t he energy range. Various dissociation patterns are proposed based on t he measurements of the ion time-of-flight differences in the PIPICO mo de. The dominant dissociation pattern is found to be Si+-Br+ and SiBr-Br+ in the whole energy examined. In the Br(3d) excitation region, ho wever, a fragmentation leading to ion pair such as SiBr3+-Br+ also pla ys an important role in the dissociation of the core-excited SiBr4. Wi th the help of ab initio Hartree-Fock and previous CI calculations, we estimate the term values and symmetries of the discrete core-excited states. This study of the specific excitation and dissociation of mole cules provides information on energy dissipation processes of the core -excited states.