No abstract

Inelastic scattering from12 C has been measured at the extremely forward angles including 0• using 386 MeV α particles to study the α-cluster states around Ex ∼ 10 MeV, especially the 2 + state predicted by the α-cluster model. We have analyzed the (α,α ′ ) cross-section data using both the peak-fitting and the multipole decomposition techniques. A 2 + state at Ex = 9.84 ± 0.06 MeV with a width of 1.01 ± 0.15 MeV is found to be submerged in the broad 0 + state at Ex = 9.93 ± 0.03 MeV with a width of 2.71 ± 0.08 MeV. This 2 + state may be interpreted as the 2 + excitation of the Hoyle state and the α-condensate state.

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.

Multipole strength distributions for isoscalar L ≤ 2 transitions in 28 Si have been extracted using 386-MeV inelastic α scattering at extremely forward angles, including 0• . Observed strength distributions are in good agreement with microscopic calculations for an oblate-deformed ground-state. In particular, a large peak at an excitation energy of 17.7 MeV in the isoscalar giant monopole resonance (ISGMR) strength is consistent with the calculations.

Proton radii of 12−19 C densities derived from first accurate charge changing cross section measurements at 900A MeV with a carbon target are reported. A thick neutron surface evolves from ∼ 0.5 fm in 15 C to ∼ 1 fm in 19 C. The halo radius in 19 C is found to be 6.4±0.7 fm as large as 11 Li. Ab initio calculations based on chiral nucleon-nucleon and three-nucleon forces reproduce well the radii.