Photodissociation and photodetachment of molecular negative ions. VII. Ions formed in CO2/O2/H2O mixtures, 3500–5300 Å

Abstract

Photodestruction cross sections have been measured for CO3−, CO3−⋅H2O, CO4−, CO4−⋅H2O, HCO3−, and HCO3−⋅H2O at various ion laser and dye laser wavelengths between 5300 and 3500 Å using a drift tube mass spectrometer as the source of the ions. CO3− shows a structureless peak centered about 4500 Å, which is attributed to photodissociation. The possible excitation of CO3− in these studies was investigated in detail and no evidence was found for any excitation. Additional evidence is presented which indicates that the bond energy D (CO2–O−) is less than or equal to 1.9 eV. The CO3−⋅H2O cross section decreases smoothly with decreasing wavelength over this wavelength range. CO4− photodestruction was observed at 3500 Å, but the other ions listed above have cross sections below 10−19 cm2, and possibly zero, throughout this spectral region.