The strength distributions of the giant monopole resonance (GMR) have been measured in the even-A Sn isotopes (A=112-124) with inelastic scattering of 400-MeV alpha particles in the angular range 0 degrees -8.5 degrees . We find that the experimentally observed GMR energies of the Sn isotopes are lower than the values predicted by theoretical calculations that reproduce the GMR energies in 208Pb and 90Zr very well. From the GMR data, a value of Ktau = -550 +/- 100 MeV is obtained for the asymmetry term in the nuclear incompressibility.

We have investigated the isoscalar giant resonances in the Sn isotopes using inelastic scattering of 386-MeV α-particles at extremely forward angles, including 0 • . We have obtained completely "background-free" inelastic-scattering spectra for the Sn isotopes over the angular range 0 • -9 • and up to an excitation energy of 31.5 MeV. The strength distributions for various multipoles were extracted by a multipole decomposition analysis based on the expected angular distributions of the respective multipoles. We find that the centroid energies of the isoscalar giant monopole resonance (ISGMR) in the Sn isotopes are significantly lower than the theoretical predictions. In addition, based on the ISGMR results, a value of K τ = −550 ± 100 MeV is obtained for the asymmetry term in the nuclear incompressibility. Constraints on interactions employed in nuclear structure calculations are discussed on the basis of the experimentally-obtained values for K ∞ and K τ .2

The strength distribution of the isoscalar giant dipole resonance (ISGDR) in 58 Ni has been obtained over the energy range 10.5-49.5 MeV via extreme forward angle scattering (including 0 • ) of 386 MeV α particles. We observe a "bi-modal" E1 strength distribution for the first time in an A < 90 nucleus. The observed ISGDR strength distribution is in good agreement with the predictions of a recent RPA calculation.

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