The spectrum of four times ionized scandium, Sc V

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 A to 220 A have been identified as combinations between 46 odd levels belonging to the 3s23p5, 3s23p44p and 3s3p53d configurations and 72 even levels of the 3s3p6, 3s23p43d, 4d, 4s and 5s 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 3s23p33d2 in the calculations of the odd parity configurations is found to be important. Almost all levels of 3s3p53d show a considerable mixing with levels of 3s23p33d2, 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). (orig.)