Sum-over-states calculations of the polarizabilities of the ground and first excited states of the lithium atom

Abstract

Approximate moments S(k) of the oscillator strength distribution are calculated by a finite sum over states. Small configuration interaction (CI) wave functions arc constructed in such a manner that the length and velocity formulas for S(−2), the static polarizability, give essentially identical results. The oscillator strengths are used to obtain the frequency dependent polarizability. Both the static and dynamic results for the lithium ground state compare favorably with values obtained with extensive CI wave functions. The method is also applied to the first excited (2P) state of lithium.