Coupled channels optical model potential for rare earth nuclei

The global spherical optical model by Koning and Delaroche is generalized to enable its use in coupled-channel calculations on well deformed nuclei in the rare-earth region. The generalization consists in adding the coupling of the ground state rotational band, deforming the potential by introducing appropriate quadrupole and hexadecupole deformations and correcting the optical model potential radius to preserve the volume integral of the spherical optical potential. We choose isotopes of three rare-earth elements (W, Ho, Gd), which are known to be nearly perfect rotors, to perform a consistency test of our conjecture on integrated cross sections as well as on angular distributions for elastic and inelastic neutron scattering. The only additional input are experimentally determined deformations, which we employ without any adjustments. The results are clearly superior compared to the spherical optical model calculations with dramatic improvement at low incident energies.