Radiative and non-radiative decays of doubly-excited configurations in the Ar7+spectrum

A configuration-average method is developed to investigate the properties of multiply-excited configurations of many-electron ions produced during multiple-electron capture collisions. For doubly-excited configurations of Ar 7+ lying below the 2p 5 5s ionisation limit, the average energy is calculated and a classification into core-excited Rydberg series is presented. The energy range spanned by Wannier-type configurations 2p 5 N'n with N approximately=n also includes high members of the Rydberg series with N<<n. The radiative and non-radiative decay rates are calculated and the cascade processes from excited configurations are analysed explicitly. The stabilisation ratio R(N', n), defined as the probability of reaching non-autoionising configurations of Ar 7+ during the cascades from the configuration 2p 5 N'n, is calculated for all configurations with N<or=5, n<or=9. Its dependence on the quantum numbers N, n, and on the energy of the configuration is investigated. Highly-excited configurations with very asymmetrical excitation of the two electrons (N<</n, '<<) correspond to high R ratios.