Quadrupole and hexadecapole moments of 232Th and 238U from inelastic scattering of 65 MeV polarized protons.

Abstract

Differential cross sections and analyzing powers of elastic and inelastic scattering of polarized protons from actinide nuclei ${(}^{232}$Th and $^{238}\mathrm{U}$) have been measured for the first time. A coupled-channel analysis has been performed for ${J}^{\ensuremath{\pi}}$${=0}^{+}$--${6}^{+}$ members of the ground state rotational band. Excellent fits have been obtained up to the ${6}^{+}$ state. Extracted quadrupole moments of the deformed optical potential are 1.0--2.0 % larger than those of the charge distribution. This difference is significantly small, compared with the case of the previous rare-earth region nuclei at 65 MeV (4--5 %). A realistic folding calculation based on the density- and energy-dependent effective interaction was performed. The effect of the Coulomb potential through the energy dependence of the effective interaction was found to be important to reproduce quadrupole moments of the deformed optical potential, especially for the actinide nuclei. Extracted hexadecapole moments are 14--18 % larger than those of the charge densities, and the possible sources of this difference in the hexadecapole moments will be discussed.