VUV-fluorescence spectroscopy of O2 photodissociation into neutral excited fragments between 17 and 19 eV

Photodissociation processes of O2 at exciting-photon energies between 17 and 19 eV were investigated through dispersed fluorescence excitation spectra in the VUV spectral range, by measuring the intensities of fluorescence lines emitted by neutral excited dissociation fragments between 90 and 105 nm as a function of the exciting-photon energy. The dissociation processes were found to be strongly influenced by predissociation of molecular Rydberg states converging to the O2+ b 4Σg− state, whereas direct dissociation processes resulting from repulsive potentials in the Franck–Condon region were found to be weak. The measured fluorescence excitation functions as a measure for O2 photodissociation were compared with photoionization and ion pair formation cross sections and it was found that the fluorescence excitation functions show similarities to the ion pair formation cross sections.