Knight Shift in Sodium-Ammonia Solutions

Two wave functions have been obtained for the electrons in sodium-ammonia solutions by a numerical procedure from two potential wells based on the model proposed by Becker, Lindquist, and Alder for metal-ammonia solutions. These wave functions have been used to calculate the expected Knight shift in the region <0.5 molar by means of an n-electron formalism previously found successful in treating the hyperfine interaction of F centers. The results have been compared with the experimental values of McConnell and Holm for the Knight shifts of Na and N in sodium-ammonia solutions, and agree quite favorably. In particular, these calculations show that the N resonance shift will decrease with dilution, while the Na shift will increase with dilution, between 0.5 and 0.03 molar. The H shift is shown to be less than 10—6 for all concentrations <0.5 molar, giving an explanation why it was not experimentally observed. Dependence of the Knight shift upon concentration is predicted for the range <0.05 molar, which has not yet been covered by experiment.