NiXI electron collisional excitation

The target includes all the main configurations up to n=4, and is a significant improvement over earlier R-matrix (only three n=3 configurations) and distorted-wave (DW) calculations. We find significant enhancements in the collision strengths of many of the strong transitions to the n=3,4 levels.

They are due to the resonances that arise within the present large-scale target. This results in significant increases in the predicted intensities of the UV and visible forbidden lines within the 3s^2^ 3p^5^ 3d configuration, the strong EUV lines that result from the decays of the 3s^2^ 3p^5^ 3d levels to the ground state, and the decays from the n=4 levels, which are visible in the soft X-rays. We find good agreement between predicted and observed line intensities in the EUV.