VERTICAL DOUBLE-IONIZATION OF THE SULFUR-DIOXIDE MOLECULE

Vertical double-ionization energies, for transitions from the ground s tate of the neutral sulphur dioxide molecule to both singlet and tripl et energetically low-lying electronic states of the SO22+ dication, ha ve been studied both experimentally with double-charge-transfer spectr oscopy and theoretically with ab initio propagator calculations; consi stently good agreement is found between the theoretical and experiment al results. The experimental data for transitions to singlet states of SO22+ are also found to be consistent with the results of earlier stu dies of SO2 employing Auger spectroscopy, which also match closely the theoretical predictions in the higher-energy range not currently acce ssible with double-charge-transfer spectroscopy. The results of this p aper, therefore, provide a comprehensive survey of the vertical double ionizations of SO2 up to 50 eV in energy, allowing an analysis of som e earlier PIPICO data for SO2. (C) 1998 Elsevier Science B.V. All righ ts reserved.