Coulomb Displacement Energies Derived from the p, n Isobaric Reaction

The agreement of Coulomb displacement energies derived from the nonmirror (p,n) isobaric reaction with those obtained from mirror and nonmirror (T=1) nuclei beta decay has been previously demonstrated. Using the Livermore 90-in. cyclotron time-of-flight facility, we have measured additional Coulomb displacement energies in the mass region 70≤A≤108. These measurements indicate possible shell effects which were previously not observed because of the paucity of data. With the availability of 20.5-MeV protons, Coulomb displacement energy measurements were extended to the mass region A≤165. Even for nuclei as heavy as Ho165, where the Coulomb displacement energy is 16.6 MeV, the width of the isobaric neutron group was not measurable (≤150 keV). The variation of the uniform radius parameter with atomic weight (A) inferred from these data is compared with that obtained from high-energy electron scattering experiments and is found to be in substantial agreement. A semiempirical formula for calculating Coulomb displacement energies is presented.