Photodissociation of positive and negative ions formed in O2

Abstract

The tandem quadrupole photodissociation mass spectrometer has been used to study photodissociation reactions of O₂⁺, O₃⁺, O₄⁺, O₂⁻, and O₃⁻ formed in O₂ at pressures between 0.01–1 torr. At low pressures O₂⁺ photodissociation was observed using 600 nm radiation, and pressure studies indicate that an excited state of O₂⁺ is involved, which is collisionally relaxed with a rate constant of approximately 2×10⁻¹¹ cm³/sec. Photodissociation of O₃⁺ was found to occur at ∼600 nm primarily by the reaction O₃⁺→O⁺+O₂ with a large cross section (10⁻¹⁷ cm²).