Dipolar dissociation dynamics in electron collisions with oxygen molecules

The dipolar dissociation of molecular oxygen due to 21-35 eV energy electron collision has been studied using the time sliced velocity map imaging technique. A rough estimation about the threshold of the process and the kinetic energy and angular distribution of the fragment negative ions are measured. The dipolar dissociation found to be occur due to pre-dissociation of a Rydberg state via ion-pair state for lower incident electron energies as well from also direct excitation to the ion-pair states for relatively higher primary beam energy. The location and symmetry of the excited states were determined from the kinetic energy and angular distribution data respectively.