The Spectrum of Three Times Ionized Scandium, Sc IV

Spectrograms from a sliding spark have been taken in a 5 m grazing-incidence spectrograph and a 3 m normal-incidence spectrograph. About 300 lines from 180 Å to 2 500 Å have been identified as ScIV lines and measured with an accuracy of ±0.004 Å in the grazing-incidence region (160-320 Å) and of ±0.008 Å in the other region. In addition, about 100 ScIV lines have been identified between 2 350 and 10 000 Å on spectrograms taken by J. E. Holmström [5] in this laboratory in a Jarrell-Ash spectrograph having a 21 ft concave grating in Wadsworth mounting. As a result of the analysis almost all the levels belonging to 3 s 2 3 p 5 4 s , 5 s , 6 s , 7 s , 4 p , 5 p , 3 d , 4 d , 4 f , 5 g , 6 g , 6 h , 7 h , 7 i and 3 s 3 p 6 3 d are established. By using the polarization formula the ionization limit has been determined from the configurations 5 g , 6 g , 6 h , 7 h and 7 i to 592 732.4±3.0 cm -1 .