Vibrationally selected O+-O+ fragmentation of O-2 below the adiabatic double-ionization potential studied via electron-electron coincidence spectroscopy

Mechanisms for O2 photofragmentation leading to the formation of the O+-O+ ion pairs, at photon energies below the adiabatic double-ionization threshold, have been investigated using a threshold-photoelectron-photoelectron coincidence technique. The selectivity and high efficiency of the experimental technique have allowed the process to be followed step by step. The measurements show that fast dissociation of a singly charged ion, followed by atomic autoionization, is the dominant decay route in this energy region.