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

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 $l=3\mathrm{}$ 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 (∼20%) is only about one half that predicted by randomphase-approximation calculations.