Observation of the High-Energy Octupole Giant Resonance with 800-MeV Protons

Abstract

Inelastic scattering of 800-MeV protons from $^{40}\mathrm{Ca}$, $^{116}\mathrm{Sn}$, and $^{208}\mathrm{Pb}$ shows a broad giant resonance at an excitation energy of $\frac{110}{{A}^{\frac{1}{3}}}$ MeV. The angular distributions are consistent only with scalar-isoscalar $l=3$ transfer. The excitation energy and width of this high-energy octupole giant resonance are in reasonable accord with theory. However, its energy-weighted sum-rule strength (\ensuremath{\sim}20%) is only about one half that predicted by randomphase-approximation calculations.