The Spectrum of Na III between 380 and 180 Å

The spectrum of doubly ionized sodium, Na III, has been investigated between 380 and 180 Å by means of a newly designed 5-meter grazing incidence vacuum spectrograph, having a plate factor of 0.4 Å/mm in the 1st order at 200 Å. About 90 Na III lines have been measured of which more than 50 are reported for the first time. The resonance lines have been measured in the 2nd, 3rd, and 5th orders and a 2 s 2 p 6 2 S -2 s 2 2 p 4 3 p combination in the first order of a 3-meter normal incidence vacuum spectrograph against Ar II standards. The results have been used to locate the 2 p 4 ( 3 P , 1 D )3 s , 3 p , 3 d , 4 s level system in relation to the ground term. Accurate wavelengths in the 273-195 Å range have been calculated. The analysis has been extended as regards the ( 3 P , 1 D )5 s levels and revised and extended as regards ( 3 P , 1 D )4 d levels with low J values.