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Abstract: High level electronic structure calculations on the OCS2+ dication made by the spdfg cc-pV5Z/CASSCF/MRCI method are presented. They enable a detailed interpretation of the newly recorded spectra of this ion made by the time-of-flight photoelectron photoelectron coincidence (TOF-PEPECO) method, and provide a reliable basis for analysis of its dissociation pathways. The major dissociation to CO+ +S+ appears to occur not on the ground state surface, but from an excited electronic state. Possible involvement of the CSO2+ isomer in dissociation is discussed. [Copyright &y& Elsevier]

Abstract: The present work combines experimental and theoretical investigations of HCN2+ to investigate the spectroscopy and dissociation dynamics of this dication. Its spectrum is a complex blend of overlapping features, consistent with theoretical calculations showing that the low-lying electronic states of HCN2+ exhibit Renner–Teller and vibronic interactions. The double ionisation spectra are dominated by C–N stretching excitations for all the electronic states investigated. Long-lived HCN2+ ions are observed and are believed to be in low vibrational levels of the X3Σ− and/or 1Δ and/or 1Σ+ electronic states; some have metastable lifetimes of about 25 ns. The formation of H++CN+ products is attributed to predissociation by the lowest 3A″ component resulting from a conical intersection between the X3Σ− and 3Π states. The overall predissociation processes involve vibronic, Renner–Teller and spin–orbit couplings between several electronic states of HCN2+. [Copyright &y& Elsevier]

Single-photon multiple ionization processes of acetaldehyde (ethanal) have been experimentally investigated by utilizing a multi-particle coincidence technique based on the time-of-flight magnetic bottle principle, in combination with either a synchrotron radiation source or a pulsed helium discharge lamp. The processes investigated include double and triple ionization in the valence region as well as single and double Auger decay of core-ionized acetaldehyde. The latter are studied site-selectively for chemically different carbon core vacancies, scrutinizing early theoretical predictions specifically made for the case of acetaldehyde. Moreover, Auger processes in shake-up and core-valence ionized states are investigated. In the cases where the processes involve simultaneous emission of two electrons, the distributions of the energy sharing are presented, emphasizing either the knock-out or shake-off mechanism. [ABSTRACT FROM AUTHOR]

Abstract: All the different Auger decay paths of Argon 2p holes have been characterized using a time of flight spectrometer of the magnetic bottle type. All electrons (the photoelectron and up to three Auger electrons) are detected in coincidence and resolved in energy. Double Auger decay is shown to proceed either through a direct process or by intense cascade paths, implying highly excited autoionizing Ar2+ states, which are identified as Ar2+ 3s−2 correlation satellites. Triple Auger decay is also observed and estimated to account for 0.2% only of all Auger decay. [Copyright &y& Elsevier]

Abstract: Double photoionisation spectra of ethyne and ethyne-d2 have been measured by the TOF–PEPECO technique and by the TPEsCO method with vibrational resolution. With the help of new calculations of the dication structure and Franck–Condon factors we deduce adiabatic double ionisation energies for the first three states of the normal hydrogen isotopomer as 31.74eV (X3Σg-), 32.42 (a1Δg) and 33.07 (b1Σg+). The two techniques give spectra with very different vibrational structure and reasons for the difference are discussed. [Copyright &y& Elsevier]

Resonant and normal Auger electron spectra associated with an O1s initial vacancy of the O2 molecule have been recorded using photon energies of 541.80, 541.97 and 650 eV. The resonant Auger spectra obtained at 541.80 and 541.97 eV are interpreted as composed essentially of two characteristic parts, one between 10 and 35 eV binding energy reminiscent to direct photoionisation, and another, above 35 eV, associated primarily with spectator decay of the intermediate core-hole state. The spectra above 35 eV owe some similarity to the ordinary Auger electron spectrum recorded at 650 eV, and an interpretation is made in terms of Rydberg series in the cation converging towards the dicationic ionisation limits. The interpretation is based on a relaxation model introduced earlier for atomic resonant Auger spectra. The assignments of the resonant spectra assume that the relevant intermediate neutral states at 541.80 and 541.97 eV governing the Auger decay are essentially the ν=0 and 1 vibrational components of the (O1s)−1 4pσ Rydberg state. Arguments for this interpretation are given. [Copyright &y& Elsevier]