The Spectrum of Four Times Ionized Scandium, ScV

The spectrum of four times ionized scandium emitted from a sliding spark discharge has been observed using a 3 m normal incidence spectrograph and a 5 m grazing incidence spectrograph. About 450 lines in the wavelength region 160 Å to 2200 Å have been identified as combinations between 46 odd levels belonging to the 3 s 2 3 p 5 , 3 s 2 3 p 4 4 p and 3 s 3 p 5 3 d configurations and 72 even levels of the 3 s 3 p 6 , 3 s 2 3 p 4 3 d , 4 d , 4 s and 5 s configurations. Of the previous identifications we have confirmed 18 levels. The level structure of the observed configurations has been theoretically interpreted by including configuration interaction effects. The inclusion of 3 s 2 3 p 3 3 d 2 in the calculations of the odd parity configurations is found to be important. Almost all levels of 3 s 3 p 5 3 d show a considerable mixing with levels of 3 s 2 3 p 3 3 d 2 , in some cases by as much as 50%. The energy parameters determined from least-squares fits to the observed level values are compared with Hartree-Fock calculations. The ionization energy is estimated to be 739 500 ± 1000 cm -1 . (91.65 ± 0.12 eV).