8 The aluminum isoelectronic sequence

8.1 Ni XVI

The [3s 2][3p ], [3s3p 2], [3s 2][3d ], [3p 3] and [3s3p3d ] configurations are included in the CHIANTI model for Ni XVI, corresponding to 40 fine-structure energy levels. Experimental energy levels come from the NIST database (Martin et al. 1995), but unfortunately no entry is found for any of the [3s3p3d ] levels. All the data are taken from Bhatia & Doschek (1998b), reporting theoretical energy levels, radiative transition probabilities and collision strengths for all possible transitions between the included 40 levels.

Collision strengths have been calculated for five values of the incident electron energy (10 to 50 Ry) using the Distorted Wave approximation. To our knowledge, this is the first large scale calculation for Ni XVI collision strengths. Close Coupling calculations are in progress at the University College of London (Storey 1998) and these will be assessed as soon as they are available.

The only Ni XVI comprehensive radiative transition probabilities calculations we are aware of are those by Huang (1986), showing reasonable agreement with the Bhatia & Doschek (1998b) values.