Photodetachment of electrons from Group IVa binary hydride anions: The electron affinities of the SiH3 and GeH3 radicals

Abstract

Relative photodetachment cross sections have been determined for the silyl and germyl anions $({\mathrm{SiH}}_3^{-},{\mathrm{GeH}}_3^{-})$ in the wavelength ranges 400.0–870.0 nm (3.10–1.43 eV) and 400.0–720.0 nm (3.10–1.72 eV), respectively. An ion cyclotron resonance spectrometer was used to generate, trap, and detect the negative ions, and a 1000 W xenon arc lamp with a grating monochromator was employed as the light source. Both ions exhibited cross sections behaving sigmoidally over the wavelength ranges studied. These experiments afford the following electron affinities: E.A. (SiH₃·) ≤1.44±0.03 eV and E.A. (GeH₃·) ≤ 1.74±0.04 eV. From estimates of proton transfer equilibrium constants, bond energies are approximated for silane and germane.