6 The oxygen isoelectronic sequence

6.1 AlVI

The n=2 configurations [2s 2][2p 4], [2s2p 5] and [2p 6] have been included in the CHIANTI database, corresponding to 10 fine-structure energy levels. The experimental energy levels come from the NIST database (Martin et al. 1995).

Radiative transition probabilities for the ground configuration are taken from Galavis et al. (1997), while allowed A values come from Fawcett (1986a). Butler & Zeippen (1994) provide thermally-averaged collision strengths for the ground level transitions over a large temperature range. These calculations were performed using the Close Coupling approximation as part of the Iron Project. There are no other sources of collisional data in the literature, and so for transitions involving the levels of the [2s2p 5] and [2p 6] configurations, the data have been interpolated from other oxygen-like ions already present in the CHIANTI database, using the program mentioned in Sect. 5.3.