Fermi contact interaction constants calculated from numerical hartree-fock wave functions

Abstract

Fermi contact interaction constants (ac) have been evaluated for a large number of atomsusing the numerical Hartree-Fock wave functions of Froese [ 13. Agreement between the calculated and the experimental values of a, is rather poor, indicating Hartree-Fock functions cannot be used to describe accurately the electronic spin density at the nucleus. General TheoryFermi [l, 21 has proved that the interaction between the magnetic moment ( p r ) of a nucleus (with nuclear spin angular momentum I) and the magnetic moment of an electron gives rise to a term in the hyperfine structure splitting (hfs) of the atomic energy levels. This interaction is effective only at very short ranges and is termed the Fermi contact ierm. As s-type electrons are the only ones with non-zero wave functions, and thus have finite non-zero densities at the nucleus, these are the only electrons which contribute to the Fermi contact term. According to Fermi [l, 21 the Hamiltonian H, for the contact term can be written as:where pB and p N are the Bohr and nuclear magnetons, ge and gn are the electronic and nuclear gyromagnetic ratios for the electron and the nucleus related to magnetic moments (p8 and p I , respectively) by the relations: *