Electron emission from aligned superexcited O-* atoms produced in photodissociation of O-2 in the 22.20-22.36 eV region

Photoelectron photoion coincidence and threshold photoelectron photoion coincidence time of flight spectra for O-2 molecules in the 22.20-22.36 eV region have been measured to investigate anisotropy in dissociative photoionization processes. Some of the Of ions were produced in a particular photodissociation process in which the molecule fragments into an O(P-3) atom and an excited O*[P-2(o) 3d('')] atom, which autoionizes to produce O+(D-2(o)) + e(-)(0.16 eV). The O+ spectra present a nonisotropic profile which is interpreted as the result of a photodissociation process producing aligned O* atoms followed by ejection of an electron along the axis of the dissociating molecule.