Photodissociation and photodetachment of molecular negative ions. II. Ions formed in oxygen

Abstract

Total photodestruction cross sections for O⁻₂, O⁻₃, and O⁻₄ ions have been measured over a photon energy range of 1.93–2.71 eV using a drift tube mass spectrometer coupled with an argon ion laser and a tunable dye laser. The O⁻₂ ion is found to photodetach at these photon energies with a cross section which varies from 1.2 to 2.2×10⁻¹⁸ cm². The O⁻₃ ion photodissociates to form O⁻ over this energy range with a cross section which varies from 0.1 to 7.3×10⁻¹⁸ cm² and exhibits structure indicative of the vibrational levels of a predissociating excited state. Structure is also observed in the O⁻₄ photodestruction cross section which varies from 1.0 to 2.2×10⁻¹⁸ cm², and in the O⁻₂ photodetachment cross section.