Dissociative electron attachment to H₂S probed by ion momentum imaging

Abstract

The dissociation dynamics of negative ion resonance states in H₂S formed upon electron attachment are studied using momentum imaging of the fragment H⁻ and S⁻ ions and compared with similar resonances in water. The H⁻ momentum images show that dissociation dynamics at the 5.2 eV resonance are very similar to those of the 6.5 eV (B₁) resonance in water. Unlike the 8.5 eV resonance in water, which has A₁ symmetry but is found to display considerable deviation from the axial recoil approximation in the momentum distribution of H⁻ ions, the distribution from the corresponding resonance in H2S at 7.5 eV is found to follow the axial recoil approximation fairly well. The resonance state with B₂ symmetry at 10 eV is found to decay via four dissociation channels viz.—H⁻ + H + S, H⁻ + SH(A²Σ), H⁻ + SH(X²Π) and S⁻ + H + H channels, similar to those that were seen in the B₂ resonance in water at 12 eV, including sequential fragmentation in the multiple fragmentation channels. However, the angular distributions for the fragment ions from this resonance are found to be distinctly different from those in water, even while displaying considerable deviation from the axial recoil approximation similar to that in water.