Single and double electron-impact ionization of chlorine dioxide

Abstract

Electron-impact single and double ionization of chlorine dioxide, OClO, have been investigated using time-of-flight mass spectrometry and ion–ion coincidence techniques. Relative partial single ionization cross sections of OClO have been determined for incident electron energies from 30 to 450 eV using time-of-flight mass spectrometry. The experiments detect stable parent ions, OClO+, and the fragmentation products O+, O2+, Cl+ and ClO+. The formation and fragmentation of the OClO dication has been investigated using ion–ion coincidence techniques coupled with time-of-flight mass spectrometry. The coincidence spectra show that OClO2+ dissociates to form the following pairs of ions: O++ClO+ and O++Cl+. Interpretation of the coincidence spectra suggests that there is a multiple kinetic energy release upon dicationic dissociation to form the O++Cl+ ion pair, and also yields a determination of the excitation energy required to form the lowest energy dication electronic states which dissociate to form O++ClO+ and O++Cl+. The similarity of these excitation energies indicate that these dissociation reactions might occur from the same electronic state of OClO2+. Comparison of these excitation energies with estimated values of the double ionization energy of OClO indicate that this state is probably the ground electronic state of OClO2+ and, hence, these investigations provide a first estimate for the double ionization energy of OClO.