  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.
