Photoelectron spectroscopy of reactive intermediates using synchrotron radiation

Experiments performed with a purpose built spectrometer to study reactive intermediates with synchrotron radiation are described. Results are presented for some short-lived molecules of atmospheric and combustion importance. Constant ionic state (CIS) and photoelectron spectra were recorded. In each case, the observation of resonant structure in the CIS spectrum enabled the identification and characterisation of Rydberg series associated with excited neutral states to be carried out. Examples of window resonances (SO) and possible competition between autoionisation and predissociation (O-2(a(1)Delta(g))) are encountered. Photoelectron spectra recorded at selected resonant energies exhibited extended vibrational structure, which led to improved estimates of ionic state spectroscopic parameters (omega(e), omega(e)x(e)). Franck-Condon calculations for both CIS and PES data provided confirmation of resonant state assignments. Preliminary angular distribution measurements performed on O-2(a(1)Delta(g)) are presented, where the asymmetry parameter (beta) showed structure at energies corresponding to neutral state resonances. (C) 2000 Elsevier Science B.V. All rights reserved.