Contribution of Core Polarization to the Atomic Hyperfine Structure and Knight Shift of Li and Na

The effect of exchange forces on the wave functions of an atom resulting from the unpaired spin of a single electron outside closed shells is considered. Calculations were carried out for lithium and sodium starting from the usual self-consistent field wave functions using a modified type of perturbation theory. These yield an increase of 31% for Li and 5½% for Na in the value of the hyperfine coupling constant. In addition, the effect of this core polarization on the theory of the Knight shift in metals is developed in detail.