Single and double electron-impact ionization of dichlorine monoxide (Cl 2O)

Abstract

Electron-impact single and double ionization of dichlorine monoxide (Cl 2O) have been investigated using time-of-flight mass spectrometry and ion–ion coincidence techniques. Relative partial single ionization cross sections of Cl 2O have been determined for incident electron energies from 30 to 450 eV using time-of-flight mass spectrometry. The experiments detect stable parent ions, Cl 2O +, and the fragmentation products Cl +, ClO +, and Cl 2 +. The formation and fragmentation of the Cl 2O dication has been investigated using ion–ion coincidence techniques coupled with time-of-flight mass spectrometry. The coincidence spectra show that Cl 2O 2+ dissociates to form the following pairs of ions: Cl + + Cl +, O + + Cl + and Cl + + ClO +. Interpretation of the coincidence spectra suggests that there is a multiple kinetic energy release upon dicationic dissociation to form O + + Cl +, indicating that two distinct electronic states of Cl 2O 2+ dissociate to form this ion pair. The experiments also yield a determination of the excitation energy required to form the lowest energy dication electronic state (30.6 ± 1 eV) which dissociates to form Cl + + ClO +. Comparison of this excitation energy with estimated values of the double ionization energy of Cl 2O indicates that this state is probably the ground electronic state of Cl 2O 2+ and, hence, these investigations provide a first estimate for the double ionization energy of Cl 2O.