Atomic multipole polarizabilities in the extended Coulomb approximation

Abstract

A new and computationally convenient exact analytic expression for the 2l-pole static polarizabilities of mono and divalent atoms and ions is obtained within the extended Coulomb approximation of Adelman and Szabo. In this approximation the valence electron wavefunction is represented by an asymptotically valid Whittaker function with hydrogenic normalization and the l-symmetry excited orbitals are eigenfunctions of a Coulombic Hamiltonian plus an r−2-type pseudopotential. Our expression for the polarizability contains two parameters which can be obtained from the ionization potentials of the ground state and the first l-symmetry excited state of the system. Illustrative calculations for the alkali and alkaline earth atoms are present. Good agreement is found with recent experimental results as well as those from elaborate calculations using correlated wavefunctions, where such results are available.