Photodissociation and photodetachment of molecular negative ions. VI. Ions in O2/CH4/H2O mixtures from 3500 to 8600 Å

Abstract

The photodestruction cross sections for O⁻, O₂⁻, O₂⁻⋅H₂O, O₃⁻, O₃⁻⋅H₂O, O₄⁻, OH⁻, and OD⁻ have been measured in the 3500–5400 Å and 6300–8600 Å wavelength regions. The ions were produced in a drift tube mass spectrometer and interacted with a dye laser or ion laser inside the laser cavity. The photodetachment cross sections for O⁻ and OH⁻(OD⁻) have sharp onsets at wavelengths near 8480 and 6795 Å, respectively, and at shorter wavelengths their values are nearly constant. The photodestruction cross sections for O₂⁻, O₄⁻, and O₂⁻⋅H₂O increase monotonically with increasing photon energy. In contrast, in the photodestruction cross section for O₃⁻, structure is observed over this wavelength region. The processes for creation and photodestruction of the various negative ions are discussed. Comparison is made with other measurements.