R.E. Shamu

Effect of nuclear deformation on neutron elastic scattering

Abstract The scattering of neutrons from 148 Sm and from 154 Sm has been studied at 6.25 MeV. Evidence is presented that the main effect of nuclear deformation on neutron elastic scattering is to decrease appreciably the scattering at back angles.

Quadrupole moments and nucleon excitation strengths in even-A Sm isotopes

Abstract We present a coherent coupled-channel analysis of 7 MeV neutron and 16 MeV proton elastic and inelastic scattering from 148, 152, 154 Sm. The optical potential and nuclear deformation parameters are determined so as to fit not only these elastic and inelastic scattering data but also the low-energy neutron scattering properties and the total cross sections over a wide energy range. This analysis provides evidence of the same excitation strengths for both projectiles in the case of 152, 154 Sm, and of a smaller excitation strength for the proton than for the neutron in case of 148 Sm. Moreover the quadrupole moments of these deformed optical potentials are in good agreement with those extracted from Coulomb excitation measurements and from nuclear matter distribution calculations.

Effects of Nuclear Deformation on Neutron Total Cross Sections

Abstract Neutron total cross section differences have been determined for 150,152,154 Sm from 0.8 to 15 MeV by measuring transmission ratios. Significant differences were observed for 152,150 Sm and for 154,150 Sm. Evidence is presented that these results can be attributed to nuclear deformation.

Quadrupole deformation parameters of 148,152,154Sm determined from neutron total cross sections

Abstract Quadrupole parameters of the nuclear potential were determined for 148, 152, 154 Sm using coupled-channel calculations. the μ 2 values for 152, 154 Sm are about 10 percent lower than μ 2 values for the nuclear charge distribution obtained from Coulomb excitation, electron scattering, and μ-meson X-ray experiments.

Nucleon scattering from 208Pb at low and intermediate energies

Abstract A phenomenological optical model analysis of neutron 208 Pb data from 2 to 250 MeV has been performed. The energy dependence of the real potential strength was found to be linear up to about 60 MeV and logarithmic above that energy. The strength of the real isovector potential, determined from a comparison with proton- 208 Pb results, was found to have a negligible energy dependence below about 50 MeV.

The one-phonon octupole vibration of 151Eu

Abstract A multiplet based on the one-phonon octupole vibration of 151Eu has been observed near 900 keV by inelastic deutron scattering. The magnitude of the splitting and the relative intensities of the multiplet states are consistent with the weak-coupling model.

Optical model potential for neutrons in the resonance region

Abstract A method is described for determining the strength of the complex central optical potential directly from neutron total cross sections measured below the threshold for inelastic scattering. Real and imaginary strengths deduced for 208 Pb are consistent with higher-energy results and are shown to provide a good fit to above-threshold data.

Symmetry dependence of the phenomenological optical model for neutron-nucleus scattering

We have determined the symmetry dependence of the central part of the phenomenological optical model potential for neutron-nucleus scattering from about 15 to 65 MeV. In contrast to the case for incident protons, we find evidence that the symmetry dependence of the surface imaginary potential is negligible. When extended to higher energies, predictions of the model are in good agreement with measured neutron total cross sections for spherical nuclei over a wide range of A and incident energy with no adjustment of parameters.