Photodissociation of positive and negative ions formed in O2

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).