Photoelectron spectroscopy of reactive intermediates using synchrotron radiation

Experiments performed with a purpose built spectrometer to study reactive i ntermediates with synchrotron radiation are described. Results are presente d 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 th e identification and characterisation of Rydberg series associated with exc ited neutral states to be carried out. Examples of window resonances (SO) a nd possible competition between autoionisation and predissociation (O-2(a(1 )Delta(g))) are encountered. Photoelectron spectra recorded at selected res onant energies exhibited extended vibrational structure, which led to impro ved estimates of ionic state spectroscopic parameters (omega(e), omega(e)x( e)). Franck-Condon calculations for both CIS and PES data provided confirma tion of resonant state assignments. Preliminary angular distribution measur ements performed on O-2(a(1)Delta(g)) are presented, where the asymmetry pa rameter (beta) showed structure at energies corresponding to neutral state resonances. (C) 2000 Elsevier Science B.V. All rights reserved.