A 2-DIMENSIONAL STUDY OF THE AUTOIONIZING DECAY ROUTES OF RYDBERG STATES CONVERGING ON THE C-2-SIGMA(+) IONIZATION THRESHOLD IN N2O

The autoionizing decay pathways of the five-dipole allowed Rydberg ser ies converging on the C-2 Sigma(+) threshold in N2O have been investig ated using two-dimensional photoelectron spectroscopy. Measurements of electron yield as a function of both electron and photon energy have been carried out using tuneable synchrotron radiation. The vast majori ty of vibrational levels of the three bound electronic states of the i on that are accessible to the decaying Rydberg states have been studie d with an experimental resolution of approximately 30 meV. This was su fficient to study transitions to individual vibrational levels. The co mprehensive nature of the data presented has enabled various observati ons pertaining to both electronic and vibrational selectivity in the a utoionizing decay processes to be made. The observed preference for th e decay of np sigma and np pi Rydberg states to the X-2 Pi and A(2) Si gma(+) states of the ion respectively may be explained if the emitted electron conserves its angular momentum. Members of the nda series res ult in the most intense features in the spectrum of the only available ion state (B-2 Pi) that has a nuclear arrangement which is significan tly different from that of the autoionizing states. It appears that di ssociative, neutral states are more likely to be accessed from nd pi s tates and it seems plausible that these dissociative states play a rol e in the resonant population of the B-2 Pi state. There is also eviden ce to suggest that this B-2 Pi State has a bent equilibrium geometry.