Ab initio calculation of atomic negative-ion states in the polarized frozen-core approximation. I. The attachment energies for O-(2P0) and C-(4S0)

The polarized frozen-core (PFC) approximation, which describes a negative ion as an electron captured in the field of a neutral polarized core, is applied for the first time to the complex negative ions O-(2P0) and C-(4S0). The negative-ion states are represented by variationally determined antisymmetrized expansions over wavefunctions of the atomic core A, including all the terms of its ground configuration and polarized pseudostates accounting for the full polarizability of its ground state. The most important attachment correlations, which are the long-range (LR) polarization of the core and short-range (SR) correlations due to exchange and capture by the open valence shell, are thus included thoroughly at the outset.