Droplet model of the giant dipole resonance

The nuclear giant dipole resonance is discussed using a macroscopic model with two new features. The motion is treated as a combination of the usual Goldhaber-Teller displacement mode and the Steinwedel-Jensen acoustic mode, and the restoring forces are all calculated using the droplet model. The $A$ dependence of the resonance energies is well reproduced without any adjustable parameters, and the actual magnitude of the energies serves to fix the value of the effective mass $m^{*}$ used in the theory. The giant dipole resonance is found to contain a large component of the Goldhaber-Teller type of motion, with the Steinwedel-Jensen mode becoming comparable for heavy nuclei. The width $\Gamma$ of the giant dipole resonance is estimated on the basis of an expression for one-body damping.