Background-free inelastic scattering spectra have been obtained for the Sm isotopes with 400 MeV α particles at forward angles (including 0°) to investigate the effect of deformation on the ...compressional-mode giant resonances. The strength distributions for the isoscalar giant resonances (L⩽3) have been extracted for the spherical nucleus 144Sm and the deformed nucleus 154Sm. We have observed that the effects of deformation are different for the low- and high-excitation-energy components of the isoscalar giant dipole resonance in 154Sm. Evidence for the theoretically predicted coupling between the isoscalar dipole resonance and the high-energy octupole resonance is reported.
Gamow-Teller (GT) transitions in atomic nuclei are sensitive to both nuclear shell structure and effective residual interactions. The nuclear GT excitations were studied for the mass number A = 42, ...46, 50, and 54 "f-shell" nuclei in ((3)He, t) charge-exchange reactions. In the (42)Ca → (42)Sc reaction, most of the GT strength is concentrated in the lowest excited state at 0.6 MeV, suggesting the existence of a low-energy GT phonon excitation. As A increases, a high-energy GT phonon excitation develops in the 6-11 MeV region. In the (54)Fe → (54)Co reaction, the high-energy GT phonon excitation mainly carries the GT strength. The existence of these two GT phonon excitations are attributed to the 2 fermionic degrees of freedom in nuclei.
Cross sections and analyzing powers for proton elastic scattering from {sup 116,118,120,122,124}Sn at 295 MeV have been measured for a momentum transfer of up to about 3.5 fm{sup -1} to deduce ...systematic changes of the neutron density distribution. We tuned the relativistic Love-Franey interaction to explain the proton elastic scattering of a nucleus whose density distribution is well known. Then, we applied this interaction to deduce the neutron density distributions of tin isotopes. The result of our analysis shows the clear systematic behavior of a gradual increase in the neutron skin thickness of tin isotopes with mass number.
We have investigated the isoscalar giant resonances in the Sn isotopes using inelastic scattering of 386-MeV {alpha} particles at extremely forward angles, including 0 deg. We have obtained ...completely 'background-free' inelastic-scattering spectra for the Sn isotopes over the angular range 0 deg. -9 deg. 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{sub {tau}}=-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{sub {infinity}} and K{sub {tau}}.
PDF
