DISSOCIATIVE SINGLE, DOUBLE, AND TRIPLE PHOTOIONIZATION OF SILICON TETRAFLUORIDE IN THE VALENCE SHELL AND SILICON 2P REGIONS (H-NU=33-133 EV)

The photoionization of SiF4 in the valence shell and Si2p innershell regions has been studied using time-of-flight mass spectrometry and synchrotron radiation over the photon energy range 33-133 eV. Photoionization branching ratios are reported for stable singly and doubly charged ions arising from the various possible molecular and dissociative photoionization processes. The time-of-flight mass spectrometer used in the present work employs very efficient ion extraction fields and this results in very much higher relative abundances of energetic fragmentations than were reported in earlier published work [Lablanquie et al., J. Chem. Phys. 90, 7078 (1989)]. Photoion-photoion coincidence (PIPICO) techniques have been used to investigate the relative yields of Coulomb explosion decomposition products and threshold energies for dissociative double photoionization in the valence shell and silicon 2p regions. The dominant process in the Si2p region is (F+ + Si+). The PIPICO spectra show additional peaks with thresholds in the Si2p region and these structures arise from the dissociation of triply charged ions into the exit channels (F+ + SiF2(2+)), (F+ + SiF2+) and (F+ + Si2+). Of these the latter is the most probable process.