Correlation and core polarization in time-dependent Hartree-Fock theory

Abstract

The time dependent Hartree-Fock (TDHF) perturbation equations are written in a form similar to the random phase approximation and solved to first order in electron-electron interaction to demonstrate that TDHF theory yields polarizabilities and matrix elements correct to first order in correlation. It is shown for alkali atoms and two-electron ions that the contribution of correlation to the dipole matrix element may be attributed to polarization of the core electrons. The TDHF expression for the transition matrix element connecting the 1s^{2 1}S and 1snp ¹P states of a two-electron ion is shown to be identical with the Z-expansion expression of Dalgarno and Parkinson (1967) within first-order correlation. A numerical comparison is given of the correction invoked by correlation to the Hartree-Fock matrix element and that given by TDHF theory.