MULTICONFIGURATIONAL-DIRAC-FOCK CALCULATION OF THE 2S(2) S-1(0)-2S2P P-3(1) SPIN-FORBIDDEN TRANSITION FOR THE BE-LIKE ISOELECTRONIC SEQUENCE

Accurate ab initio multiconfigurational-Dirac-Fock (MCDF) calculations of the lifetimes of the spin-forbidden 2s2 1S0-2s2p 3P1 transition and the allowed 2s2 1S0-2s2p 1P1 transition in Be-like ions have been performed. The importance of the inclusion of the Breit interaction to obtain accurate fine-structure splittings and mixing coefficients is discussed and the noted discrepancy between the length and velocity gauges for the intercombination line in the lighter ions is addressed. Different optimization procedures are evaluated. For C iii the experimental intercombination transition rate has been measured to be 121.9 s-1 with an accuracy of 6%. The current calculation gives 100.3±4 s-1, in agreement with other recent calculations. © 1995 The American Physical Society.