Oscillator strengths for transitions among low-lying quartet terms in the nitrogen isoelectronic sequence

Abstract

We have calculated energies and transition rates for the 2s22p3 4S° ground state and a number of excited states in the isoelectronic sequence of atomic nitrogen using the multiconfiguration optimized potential model (MCOPM). The excited states include the 2s22p23s 4P, 2s2p4 4P, 2s22p23p 4D°, 2s22p23p 4P°, 2s22p23p 4S°, 2s22p23d 4F, 2s22p23d 4D and 2s22p23d 4P terms. The oscillator strengths for transitions among these terms have been calculated in both length and velocity gauge. Particular emphasis has been put on an accurate description near level crossings. Comparison with other theoretical and experimental results are made. However, the experimental data are rather sparse, and verification of many of the calculated trends against experiment is therefore not yet possible.