Symmetry Energy for Collective Dipole Excitation

Abstract

Results from radiative proton capture in several nuclei near $A\approx 60$ and $A\approx 90$ show that the displacement energies of the $T+1\mathrm{}$ and $T$ isospin components of the collective electric dipole states are well described by a collective symmetry energy $U=\frac{T\tilde{V}}{A}$ with a value of $\tilde{V}=58\mathrm{}\pm 5$ MeV. The specific cases of ${}_{}{}^{49}{}_{}{}^{}\mathrm{Sc}$ and ${}_{}{}^{64}{}_{}{}^{}\mathrm{Zn}$ are discussed.