THE ELECTROMAGNETIC EXCHANGE CURRENT, THE NUCLEON-NUCLEON INTERACTION, AND NUCLEAR MAGNETIC-MOMENTS

A method of constructing the electromagnetic exchange-current density operator from a given complete, energy-independent model for the nucle on-nucleon interaction, which satisfies the continuity equation to ord er (v/c)2, is developed. The resulting current operator is then used t o derive the general expression for the two-nucleon part of the nuclea r magnetic moment operator that is associated with the nucleon-nucleon interaction. The utility of this method is illustrated by a derivatio n of the general expression for this exchange-current contribution to the effective magnetic moment operator of a valence nucleon outside a closed shell in the Fermi-gas model. Numerical values for the g-factor s of the valence nucleon are calculated using two realistic models for the nucleon-nucleon interaction. The calculated exchange-current corr ections are finally combined with the corrections from the most import ant model-dependent currents to give the net exchange-current correcti on to the g-factors.