ABSOLUTE OSCILLATOR-STRENGTHS FOR PHOTOABSORPTION, PHOTOIONIZATION AND IONIC PHOTOFRAGMENTATION OF SILANE .1. THE VALENCE SHELL

Absolute photoabsorption oscillator strengths (cross sections) for the valence shell of silane have been measured using dipole (e, e) spectroscopy in the equivalent photon energy range 8-100 eV. Photoionization time-of-flight (TOF) mass spectra have been collected using dipole (e, e+ion) coincidence spectroscopy from the first ionization potential up to 52 eV. Combination of the photoabsorption oscillator strengths with the photoionization efficiency and the ionic photofragmentation branching ratios determined from the mass spectra yielded oscillator strengths for all dissociative photoionization channels. No stable molecular ions were detected. Using the measured ion appearance potentials and previously reported ionization potentials of silane, the various contributions to each of the dissociative photoionization channels arising from decomposition of the valence T2 and A1 ionic states (vertical ionization energies ≈ 12.4 (T2) and ≈ 18.2 eV (A1)) are estimated. Based on this information electronic state partial photoionization cross sections are inferred for the T2 and A1 states. © 1990.