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%'e have measured high-resolution electron decay-in-flight spectra of highly excited carbon ions, produced by 2-MeV C+ beams emerging from carbon foils. An almost complete identification for the resolved spectral lines is suggested for the prompt and time-delayed electron emission spectra. To assign the observed structures excitation energies for various core-excited states have been calculated using the generalized Brillouin theorem -multiconfiguration method of Schwarz and Chang. Experimental term energies for Coulomb and metastable autoionizing states in two-, three-, and four-electron carbon ions are tabulated and compared to calculated transition energies. Because of line blending most of the experimentally deduced term energies are uncertain to + 0.4%. Some spectral features in the high-energy portion of the prompt spectrum can be attributed to decays of doubly excited He-like carbon ions.

Two model potential approximations to the pseudopotential operator are discussed. Suitable simple expressions for an atomic model potential with angular projection are given, the parameter values of which can be fitted to reproduce the Rydberg series rather accurately. Calculations on atomic states with several valence electrons from the first two and a half rows of the periodic system show that energies of chemical interest are accurate to 0.0-0.2 eV. The pseudo-wave functions have an accuracy of a few %.