THE ROLE OF AUTOIONIZATION IN MOLECULAR-OXYGEN

Photoelectron spectra of the O-2(+) ground-state have been measured as a function of photon energy from 14.75 to 15.05 eV with monochromatic synchrotron radiation and a spectrometer incorporating a state of the art position-sensitive detector. The results cover the first 13 vibra tional levels of the X(2)II(g) ionic state and show a strong influence of the decay of the (IIu)-I-3 neutral autoionizing states I, I' and I ''. A comparison is made between the observed spectra and a model calc ulation which includes both direct and resonant mechanisms for the pop ulation of the ionic states. Based on Morse type potential curves the inter-nuclear spacing, r(e) for the I, I' and I'' states were determin ed to be 1.380(3), 1.380(3) and 1.390(5) Angstrom, respectively. Some limitations of the comparison are discussed.