Nucleon Size Contributions to the Hyperfine Structure of Hydrogen and Helium

Abstract
The effect of the electromagnetic structure of the proton and neutron upon the hyperfine splitting of S states in hydrogen and helium is calculated nonrelativistically. Convenient formulas are given, assuming that the charge and moment distributions of the proton and neutron are Gaussian. A summary of calculations of nuclear structure effects in deuterium is given and the present experimental situation is reviewed. If there is no relativistic or interaction moment contribution to the magnetic moment of the deuteron, the percent D state is 3.9, which is, under the same assumptions, consistent with the hyperfine splitting of deuterium.