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 over the range 30-133 eV. The photoionization efficiency curve of SiBr4 has been recorded as a function of the incident photon energy. Dissociation processes of SiBr4 have also been investigated by photoelectron-photoion coincidence and photoion-photoion coincidence (PIPICO) techniques. Various monocations of Br-n(+) (n = 1, 2) and SiBrn+ (n = 0-4) are detected along with dications of Br2+ and SiBrn2+ (n = 0, 1, 3) in the energy range. Various dissociation patterns are proposed based on the measurements of the ion time-of-flight differences in the PIPICO mode. The dominant dissociation pattern is found to be Si+-Br+ and SiBr+-Br+ in the whole energy examined. In the Br(3d) excitation region, however, a fragmentation leading to ion pair such as SiBr3+-Br+ also plays an important role in the dissociation of the core-excited SiBr4. With 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 molecules provides information on energy dissipation processes of the core-excited states.