2p^33s, 3p, 3d, 4s, and 4d configurations of triply ionized sodium, Na iv

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Abstract
The spectrum of triply ionized sodium, Na IV, has been studied in the 2500-1300 and 415-135 Å ranges and its analysis extended. About 55 lines in the 2160-1450 Å range have been observed and classified as 3s-3p and 3p-3d combinations, and some 25 lines are either newly observed or newly resolved in the 210-135 Å range. New levels that have been established include 18 levels belonging to the 3p configuration, 16 levels belonging to six new 3d terms, the 5S2 level of 3s, and two (2P)3P levels of 4s. For seven previously known 3s, 3d, 4s, and 4d triplet terms the fine structure has been determined: 19 out of 21 possible levels have now been established. No intercombinations between the 3s, 3p, and 3d quintet system and the singlet-triplet system have been observed. Isoelectronic comparisons in the OI, FII, NeIII, NaIV, MgV sequence have been made as have least squares fits of theoretical energy expressions to observed 3s, 3p, and 3d levels of NaIV. The 3s, 3p, and 3d configurations show good LS purity.