Vertical double ionization of the sulphur dioxide molecule

Vertical double-ionization energies, for transitions from the ground state of the neutral sulphur dioxide molecule to both singlet and triplet energetically low-lying electronic states of the SO22+ dication, have been studied both experimentally with double-charge-transfer spectroscopy and theoretically with ab initio propagator calculations; consistently good agreement is found between the theoretical and experimental results. The experimental data for transitions to singlet states of SO22+ are also found to be consistent with the results of earlier studies of SO2 employing Auger spectroscopy, which also match closely the theoretical predictions in the higher-energy range not currently accessible with double-charge-transfer spectroscopy. The results of this paper, therefore, provide a comprehensive survey of the vertical double ionizations of SO2 up to 50 eV in energy, allowing an analysis of some earlier PIPICO data for SO2. (C) 1998 Elsevier Science B.V. All rights reserved.