Photoelectron spectroscopy of SiH3- and SiD3-

The authors have measured the photoelectron spectra of SiH3- and SiD3- and report the following electron affinities: EA(SiH3) = 1.406 +/- 0.014 eV, EA(SiD3) = 1.386 +/- 0.022 eV. From an analysis of the peak splittings and intensities, we extract potential energy curves for the umbrella mode of the SiH3- negative ion and the SiH3 radical. Both species are pyramidal molecules with inversion barriers of 9000 +/- 2000 cm-1 for SiH3- and 1900 +/- 300 cm-1 for SiH3. The bond angle α(H-Si-H) for SiH3- is found to be 94.50 while the value for the radical, SiH3, is 112.50. Using the gas-phase acidity of SiH4, we obtain the following bond dissociation energy for silane: DH0298 (H3Si-H) = 90.3 +/- 2.4 kcal/mol