Energy levels, wavefunction compositions and electric dipole transitions in neutral Ca

A configuration-interaction approach, based on the use of B-spline basis se ts combined with a model potential including monoelectronic and dielectroni c core polarization effects, is employed to calculate term energies and wav efunctions for neutral Ca. Results are reported for singlet and triplet bou nd states, and some quasi-bound states above the lowest ionization limit, w ith angular momentum up to L = 4. Comparison with experiment and with other theoretical results shows that this method yields the most accurate energy values for neutral Ca obtained to date. Wavefunction compositions, necessa ry for labelling the levels, and the effects of semi-empirical polarization potentials on the wavefunctions are discussed, as are some recent identifi cations of doubly-excited states. It is shown that taking into account diel ectronic core polarization changes the energies of the lowest terms in Ca s ignificantly, in general by a few hundred cm(-1), the effect decreasing rap idly for the higher bound states. For Rydberg states with n approximate to 7 the accuracy of the results is often better than a few cm(-1). For series members (or perturbers) with a pronounced 3d character the error can reach 150 cm(-1). The wavefunctions are used to calculate oscillator strengths a nd lifetimes for a number of terms and these are compared with existing mea surements. The agreement is good but points to a need for improved measurem ents.