Observation of Giant Dipole Resonances Built on States of High Energy and Spin

Abstract

Spectra of $\gamma$ rays in the 2-30-MeV range have been observed following ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$-induced reactions leading to the ${}_{}{}^{122}{}_{}{}^{}\mathrm{Te}$, ${}_{}{}^{150}{}_{}{}^{}\mathrm{Gd}$, and ${}_{}{}^{164}{}_{}{}^{}\mathrm{Er}$ systems. Shoulders in the spectra for $E_{\gamma }>10\mathrm{}$ MeV are interpreted as arising from the giant dipole resonance and are consistent with statistical-model calculations that use the giant-dipole-resonance strength function. Their observation offers the possibility of studying nuclear shapes and dynamics as functions of temperature and spin.