A−16Dependence of Giant Dipole Energies

Abstract

Goldhaber and Teller suggested a model for the giant £1 transition resonance in which the sphere of neutrons oscillates against the sphere of protons. Using simple arguments they showed such a model predicts an A~~1 /6 dependence of the dipole energy on atomic weight. However, Steinwedel and Jensen introduced a hydrodynamic model of the nucleus with a rigid nuclear surface that predicted an A~l& behavior. They obtained a semiqualitative estimate of the energy by using as the restoring force the symmetry energy term in the semiempirical mass formula. We present a hydrodynamic model which includes a realistic nuclear surface and show that an A~1 1 * behavior is again predicted. A plot of the data for nuclei from 4 He to 238 U shows that the logco values, where 0) is the average energy of absorption for a given nucleus, fall on a straight line with slope of -f.