PHOTO-DISSOCIATION AND PHOTODETACHMENT OF MOLECULAR NEGATIVE-IONS .6. IONS IN O-2-CH4-H2O MIXTURES FROM 3500-A TO 8600-A

The photodestruction cross sections for O-, O2 -, O2-·H2O, O 3-, 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 O 3-, 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. © 1979 American Institute of Physics.