Analysis of the Spectrum of Triply Ionized Magnesium (Mg iv)

Abstract

A study of Mg iv between 80 and 2100 A has led to the classification of 243 lines. A total of 23 odd and 64 even levels have been identified as belonging to the 2s22p5, 2s22p6, 2s2p53s, 2s22p43p, 2s22p4ns, and 2s22p4nd (n = 3, 4, 5) configurations. Matrix diagonalizations and least-squares fits to the observed levels lead to well-defined radial integrals and verify the level assignments. On the basis of comparisons in the F i isoelectronic sequence, designation changes are suggested for some 2p4(3P)3d levels of Na iii, Al v, Si vi, P vii, and S viii. New levels are given for Na iii and Al v, and some previously listed levels in Na iii and S viii are rejected as unreal. An ionization energy of 880 800 cm−1 is given for Mg iv.