Giant multipole resonances from inelastic scattering of 152-MeV alpha particles

Giant resonance spectra have been measured for /sup 208/Pb, /sup 120/Sn, /sup 90/Zr, /sup 58/Ni, and /sup 46/Ti, using inelastic scattering of 152-MeV alpha particles. In addition to some low-lying states, the spectra were analyzed to yield separate peaks for the giant quadrupole resonance and giant monopole resonance, except in /sup 46/Ti, where no evidence was found for a giant monopole resonance. The results for the monopole resonance when compared to distorted-wave Born-approximation calculations show that approx.100% ( +- 20%) of the T=0, L=0 energy weighted sum rule is depleted for nuclei with A>90. For /sup 58/Ni only 40% of the monopole sum rule is found. The excitation energy of the giant monopole resonance follows the systematic trend approx.80 A/sup -1/3/ MeV. The data are also compared with folding model calculations using Tassie transition densities and an effective interaction derived from elastic data. Good agreement was obtained for low-lying quadrupole and octopole excitations, but this model yields considerably too little cross section for the monopole resonance. This probably indicates a deficiency in the Tassie model breathing mode transition density.