Elastic Scattering Of 08 335 Mev Neutrons From The Nucleus Ca40

Ratios of the cross sections for elastic scattering of 8 MeV neutrons from adjacent nuclei are measured over the angular range (almost equal to)20° - 160° for the target pairs 51V/Cr, 59Co/58Ni, Cu/Zn, 89Y/93Nb, 89Y/Zr, 93Nb/Zr, In/Cd and 2°9Bi/Pb. The observed ratios vary from unity by as much as a factor of (almost equal to)2 at some angles for the lighter target pairs. Approximately half the measured ratios are reasonably explained by a simple spherical optical model, including size and isospin contributions. In all cases, the geometry of the real optical--model potential is essentially the same for neighboring nuclei, and the real--potential strengths are consistent with the Lane model. In contrast, it is found that the imaginary potential may be quite different for adjacent nuclei, and the nature of this difference is examined. It is shown that the spin--spin interaction has a negligible effect on the calculation of the elastic--scattering ratios, but that channel coupling, leading to a large reorientation of the target ground state, can be a consideration, particularly in the 59Co/58Ni case. In the A (almost equal to) 50--60 region the calculated ratios are sensitive to spin--orbit effects, but the exact nature of this interaction must await more definitive polarization measurements. The measured and calculated results suggest that the concept of a conventional global'' or even regional'' optical potential provides no more than a qualitative representation of the physical reality for a number of cases. 48 refs., 14 figs., 3 tabs.