Astron. Astrophys. Suppl. Ser. 135, 159-169

Atomic data from the IRON Project

XXXIII. Radiative rates for the intercombination transitions in the carbon isoelectronic sequence

C. Mendoza^1,2 - C.J. Zeippen² - P.J. Storey³

Send offprint request: C.J. Zeippen

1 - Centro de Física, Instituto Venezolano de Investigaciones Científicas (IVIC), PO Box 21827, Caracas 1020A, Venezuela
2 - URA 173 (associée au CNRS et à l'Université Paris 7) et DAEC, Observatoire de Paris, F-92195 Meudon, France
3 - Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK

Received June 11; accepted August 31, 1998

Abstract:

Radiative decay rates are computed with the atomic structure code SUPERSTRUCTURE for the ${\rm 2s2p}\sp3$ $\sp5{\rm S}\sp{\rm o}_2~-~ {\rm 2s}\sp2{\rm 2p}\sp2$ $\sp3{\rm P}_1$, $\sp3{\rm P}_2$ and $\sp1{\rm D}_2$ intercombination transitions of the carbon isoelectronic sequence ($6 \leq Z \leq 28$). Contributions from configuration interaction and relativistic corrections are carefully studied, in particular the spin-spin interaction that is shown to be of considerable importance for low Z. By extensive comparisons with other theoretical datasets and measurements of the $\sp5{\rm S}\sp{\rm o}_2$ radiative lifetime and the $B=A(\sp5{\rm S}\sp{\rm o}_2~-~\sp3$P$_2)/A(\sp5{\rm S}\sp{\rm o}_2~-~\sp3$P₁) branching ratio, we are able to assign accuracy ratings to the present transition probabilities. The transitions to the ground term are believed to be accurate to better than 10% whereas the smaller A-values belonging to transitions to the $\sp1{\rm D}_2$ are not expected to be accurate to more than 20%.

Key words: atomic data