Electron-impact detachment of O3−, NO3− and SO2− ions

Abstract

Electron scattering on small negatively charged polyatomic molecules has been studied at the heavy-ion storage ring ASTRID. O₃⁻, NO₃⁻ and SO₂⁻ ions were merged with a cold electron beam, and the relative reaction cross sections were measured for collision energies in the range from 0 to about 50 eV. The absolute magnitudes of the cross sections are predicted using a classical reaction model, and we compare all previously published detachment thresholds from storage ring experiments to the electron affinities of the corresponding atomic and molecular species. A classical over-the-barrier model predicts the atomic anion thresholds well, whereas Franck–Condon factors play a role for molecular ions. Moreover, branching ratios for molecular break-up into different final channels were determined.