Precision Calculations of Atoms with Few Valence Electrons

摘要

We discuss the possibility of using pair equations for the construction of the effective Hamiltonian H_(eff) for valence electrons of an atom.The low-energy part of atomic spectrum is found by solving the eigenvalue problem for H_(eff).In this way it is possible to account efficiently for the valence-valence and core-valence correlations.We tested this method on a toy model of a four-electron atom with the core Is~2.The spectrum obtained with H_(eff) for two valence electrons is in perfect agreement with the full configuration interaction for all four electrons.