Photodetachment-photoelectron spectroscopy of disulfanide: the ground and first excited electronic state of HS2 and DS2

Abstract

Photodetachment-photoelectron spectra of HS₂⁻ and DS₂⁻ are presented. The obtained electron affinities (EA (HS₂) = 1.916 ± 0.015 eV and EA (DS₂) = 1.918 ± 0.015 eV) are in good agreement with earlier results (S. Moran and G. B. Ellison, J. Phys. Chem., 1988, 92, 1794). Photodetachment into the neutral ground state of the radicals HS₂ and DS₂ leads to excitation of the S–S stretching mode, whereas photodetachment into the first excited state causes a S–S–H bending and a weak S–H stretching motion. Additionally, weak peaks of S₂ were observed in the spectra of HS₂ and DS₂, leading to the conclusion that photodetachment with 2.77 eV (448 nm) causes dissociation of HS₂⁻ and DS₂⁻ into S₂⁻ and H/D. Taking 2.77 eV as an upper limit for D₀(S₂⁻–H) a lower limit for Δ_fH⁰(HS_{2 (g)}) of 100.8 kJ mol⁻¹ is obtained which is an improvement on the literature value of 107.145 ± 10.46 kJ mol⁻¹.