Effect of Correlation on the Hyperfine Interaction in Lithium

Abstract

The results of calculations of the hyperfine interaction in the ground state of lithium, using well-correlated wave functions, are reported. An analysis of the wave functions is made in terms of operators which resolve the general doublet function into two components, one of which is characterized by a spatially symmetric core function. The calculations show that this component with the spatially symmetric core can give very good values for both the energy (-7.47630 a. u.) and the hyperfine interaction (98.8% of experiment). The inclusion of the second doublet component and some quartet component in the wave function has very little effect on either the energy or the hyperfine interaction. These results are discussed and compared with those obtained with the unrestricted Hartree-Fock (UHF) method. The conclusion is reached that the usual interpretation of the results obtained for lithium with the UHF method is not entirely acceptable.