Asymmetry in the dissociation of O2in the core hole excited states

The angular distribution of fragment ions from O 2 following a selective K-shell excitation has been measured using a rotatable time-of-flight mass spectrometer. The asymmetry parameter characterising this distribution was found to be close to -1 at 531 eV ( pi * resonance). The parameter was about 1.2 at 541 eV (1s to 3p excitation), indicating that the transition to the sigma * resonance occurs at a probability significantly higher than that to the 3p orbital.