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Electron spectra ejected from doubly excited states of Be-like ions produced by two electron capture processes in O6+ + Ca, C4+ + Mg and C4+ + Ca collisions have been measured by means of high resolution zerodegree electron spectroscopy. For the O6+ + Ca collision, spectra from the 1s24lnl' and 1s25lnl' states are observed in addition to those from the 1s23lnl' states in which n equals six or larger. For the C4+ + Mg and Ca collisions, spectra from the 1s23lnl' and 1s24lnl' states are observed. Population distributions of the states are explained as a whole using the concept of the reaction window based on the extended classical over-barrier model by Niehaus.

Electron energy spectra arising from collisions between He-like ions (O6+ and N5+) and rare gas atoms (He, Ne and Ar) were measured using zero-degree Auger electron spectroscopy with high energy resolution. The electrons were ejected from doubly excited Be-like ions produced by double electron capture from the targets. Triplet states in the doubly excited systems were predominantly produced in O6+-Ne and N5+-Ar collisions.

Ejected electrons from doubly-excited helium atoms, produced by double electron capture collisions of He2+ with Mg, Ca and Ba atoms at low energies, have been measured using zero-degree electron spectroscopy with high energy resolution. Electrons from the configurations (2lnl') (n ≥ 2) were observed. Electron spectra from the terms of higher angular momenta are dominant in contrast to the case of ion or electron-impact excitation of neutral He.