Calculations are presented of energy level values, radiative transition probabilities and autoionisation rates for terms belonging to the ls23/31' configurations for several ions in the Be I isoelectronic sequence (C2+, N3+, 04+, Ne6+ and Xe5"+). The results of a C I calculation including the configurations of the complex (and the 3d4f configuration) are compared with experimental results obtained in collisions of highly stripped ions with He, H 2 and Ar and with the results of theoretical calculations.

The authors consider the probability for double-Auger decay of multiply-excited states in Nn+ with two 1s vacancies. They have calculated the branching ratio R3 between the double-Auger decay filling both holes in the 1s shell and the normal Auger decay for initial 2pN, 2s2pN-1 and 2s22pN-2 configurations with N=3, 4, 5 and 6. They show that R3 depends more strongly on the number of 2s electrons than on the total number of electrons in the n=2 shells. They find that the 'shake-down' of a 2s electron due to the non-orthogonality between the initial 2s and the final 1s electron is the most important effect. Comparison with the result of recent studies of neutralization of slow highly-excited ions at surfaces suggests the presence of one or two 2s electrons in the ion at the time of the double-Auger decay.

The authors report calculations of energies and decay rates for triply-excited 3l3l'3l" configurations in Li-like N, N4+, and in B-like N, N2+, using a configuration interaction approach. Triply-excited configurations can be obtained in charge-exchange experiments and might be important in the process of neutralization of slow highly-ionized ions at surfaces but nearly no spectroscopic information is available for such states. They have found that there is a very strong configuration mixing in these systems which makes it difficult to give single-particle labels to the terms. This suggests that a molecular (collective) description might be useful in analogy with the molecular model of the doubly-excited nlnl' configurations in He-like spectra. Watanabe and Lin (1987) have considered a molecular description of the 3l3l'3l" configurations in He-. The authors have considered whether this model is useful in the present case where the nuclear attraction is much stronger compared to the interelectronic repulsion but they do not find any compelling evidence for such a description.

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Results are presented for radiative and non-radiative decay rates for 3l3l'nl' states in N4+ and 2lnl' states in N5+ in a single configuration as well as in a CI approximation. It is found that while radiative stabilization is negligible for the triply-excited states, it is important for the doubly-excited states with n)6. These results are used to interpret multiple charge-exchange experiments in nitrogen by Benoit-Cattin et al. (1988). The reasons for the difference between the doubly- and triply-excited states are discussed.