Coulomb Energies and Nuclear Shapes

Abstract

One of the first estimates of nuclear radii was obtained from experimental Coulomb energies. Bethe (1), over 30 years ago, showed that the energy difference between the ground states of mirror nuclei is essentially due to a difference in electrostatic energy. Assuming spherical charge distributions of uniform density, charge radii were extracted. Many experimental and theoretical papers on Coulomb energies have appeared since, but muonic X-ray and electron scattering experiments (2,3) have contributed considerably more to the understanding of the size and shape of nuclear charge distributions. Only very recently Nolen and Schiffer (4) have reestablished the importance of Coulomb energy data for obtaining information about nuclear sizes. They showed that the Coulomb displacement energy between any nuclear state, a ground state for example, and its analogue state in the neighboring proton-rich isobar depends strongly on the radial distribution of the neutron excess in the ground state. Thus, experimental Coulomb displacement energies, now known even in heavy nuclei (5), present a powerful tool for determining distributions of neutrons.