Neutron scattering from elemental indium: Optical model and bound-state potential

Neutron elastic-scattering cross sections of indium are measured from 4.5 to 10 MeV at intervals of ∼500 keV. Seventy or more differential values are obtained at each incident energy, distributed between ∼18 degree and 160 degree. These are combined with lower-energy data previously obtained at this laboratory, and with 11- and 14-MeV results from the literature, to form a comprehensive elastic-scattering database extending from ∼1.5 to 14 MeV. These data are interpreted in terms of a conventional spherical optical model. The resulting potential is extrapolated to the bound-state regime. It is shown that in the middle of the 50--82 neutron shell, the potential derived from the scattering results adequately describes the binding energies of particle states, but does not do well for hole states. The latter shortcoming is attributed to hole states having occupational probabilities sufficiently different from unity so that the exclusion principle becomes a factor, to rearrangement of the neutron core, and to the fact that the shell-model potential was assumed to have an energy-independent geometry. The systematic behavior of the real optical potential is discussed, and it is shown that the isovector strength deduced from neutron scattering is consistent with the nucleon-nucleon scattering data when a mass dependence of the radius is used