Title: Valence double ionization of O2 at photon energies below and above the molecular double ionization threshold
Abstract: A recently developed time-of-flight photoelectron–photoelectron coincidence spectroscopy technique, which gives complete two-dimensional e−–e− spectra in single photon double ionization, is applied to molecular oxygen at photon energies below and above the adiabatic double ionization threshold of O2. Analysis of the two-dimensional coincidence maps reveals specific indirect pathways for the double ionization process. Dissociative ionization paths with subsequent autoionization of atomic oxygen are found to be the dominant processes for all chosen photon energies. Spectra of the photoelectrons coincident with the autoionization electrons show that intermediate O2+ states are involved which do not autoionize to molecular O22+. In particular, the ground state of O22+ is vibrationally resolved and shows a regular progression which can be well described by direct Franck-Condon transitions at an internuclear distance Re(XΣg+1)=1.054Å. Quantum yields of double ionization for O2, of a form discussed in this paper, are determined.
Publication Year: 2005
Publication Date: 2005-04-07
Language: en
Type: article
Indexed In: ['crossref', 'pubmed']
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Cited By Count: 47
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