The spectrum of three times ionized calcium, Ca IV

The spectrum of three times ionized calcium emitted from sliding spark discharges has been observed using 3-m normal incidence spectographs and a 2-m Ebert spectrograph. More than 500 lines have been identified in the wavelength region 295 Å to 2830 Å as combinations between 106 levels of the configurations 3 s 2 3 p 5 , 3 s 3 p 6 , 3 s 2 3 p 4 3 d , 4 s , 4 p , 4 d , 5 s and 3 s 3 p 5 3 d . The level structure has been theoretically interpreted by means of calculations including configuration interactions. Energy parameters determined from least-squares fits to the observed level values are compared with theoretical values obtained with Hartree-Fock wavefunctions from the Cowan computer code.