New insight into the Auger decay process in O2: the coincidence perspective

Photoelectron-Auger electron coincidence spectroscopy is a powerful tool for the investigation of Auger decay processes with different core-ionized intermediate states. In this paper we describe an investigation into the Auger decay of the O2 molecule, with the purpose of bringing new insight into the dynamics of the core hole decay mechanism. Using a novel experimental approach to measuring such coincidence spectra we report the highest resolution Auger spectrum of O2 recorded hitherto. In our approach, we have combined the advantages of these coincidence spectra with the high resolution and excellent signal-to-noise ratios of non-coincident Auger spectra and a state-of-the-art fit analysis. In this way we derived information about the potential energy curves of the final states W 3 u, B 3 g, and B’ 3 u and concluded that the corresponding Auger transitions are formed to a big part by strongly overlapping vibrational progressions. The present findings are compared to earlier results reported in the literature confirming some theoretical predictions. In addition, several new features are observed, which are attributed to autoionization of neutral doubly excited states.