On the Neutron-Proton Interaction

Field theories of nuclear forces predict the existence of a spin dependent interaction similar in character to the coupling energy between two dipoles. The purpose of this paper is to study the influence of such spin-spin forces on the behavior of the neutron-proton system. A phenomenological theory is developed in which are adopted simplified rectangular well potentials whose constants are determined to fit the binding energy and quadripole moment of the deuteron, and the scattering of slow neutrons in hydrogen. The range of the forces is chosen to be that deduced from proton-proton scattering. The effects investigated include the magnetic moment of the deuteron, the scattering of neutrons in hydrogen, the radiative capture of slow neutrons, and the photo-disintegration of the deuteron. Most of the effects considered can be understood as a simple consequence of the reduced amount of the ${}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}$ ground state of the deuteron occasioned by the admixture of a small percentage of a ${}_{}{}^3{}_{}{}^{}D_1^{}{}_{}{}^{}$ state. The phenomenological theory here employed adequately represents the experimental data, with the exception of the photomagnetic disintegration of the deuteron which would seem to require a detailed knowledge of the charge-bearing field.