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

Abstract

Spectra of $\ensuremath{\gamma}$ 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 ${E}_{\ensuremath{\gamma}}>10$ 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.