Photodissociation and photodetachment of Cl2−,ClO−, Cl3− and BrCl2−

Abstract

Absolute cross sections for the photodestruction of Cl₂⁻, ClO⁻, Cl₃⁻, and BrCl₂⁻ were measured over the wavelength range of 3500–7600 Å using a drift tube mass spectrometer–laser apparatus. The photodissociation cross section for Cl₂⁻ has two bands, as has been observed for the isoelectronic Ar₂⁺ ion. The wavelength dependence of these bands is used to adjust the calculated potential curves of the ion in the Franck–Condon region. The photodestruction cross section for ClO⁻ has a narrow band peaked at 4300 Å with a width of 400 Å, superimposed on a continuum that slowly increases with photon energy. The narrow band is attributed to photodissociation and the continuum to photodetachment. Cl₃⁻ and BrCl₂⁻ have no significiant photodestruction cross sections for wavelengths longer than 4700 Å. At shorter wavelengths, the cross sections increase with increasing photon energy. The photodestruction of these ions is attributed to photodissociation. The present gas phase measurements are compared with optical spectra for the ions obtained in different environments.