A dispersive optical model for n + 120Sn from −15 to +80 MeV and properties of neutron single-particle and single-hole states

Abstract

Data for σ(θ) and Ay(θ) previously obtained at the Triangle Universities Nuclear Laboratory for 120Sn(n, n) are combined with other measurements of σ(θ) and Ay(θ) to create an elastic-scattering database from 9.9 to 24 MeV. In addition, relatively recent high-accuracy measurements of the neutron total cross section σT for Sn from 5 to 80 MeV are combined with earlier σT data to form a detailed σT database from 0.24 to 80 MeV. All of these data are analysed in the framework of a dispersive optical model (DOM). The DOM is extended to negative energies to investigate properties of single-particle and single-hole bound states. The DOM also is used in calculations of compound-nucleus contributions to σ(θ), so that DOM predictions can be compared to σ(θ) measurements. Excellent agreement is obtained for the entire set of scattering data from 0.4 to 24 MeV, and for σT values from 0.05 to 80 MeV. Calculations of bound-state quantities are compared to values derived from experiment for energies down to −15 MeV. Reasonable agreement for the binding energies is achieved, while the predicted spectroscopic factors disagree somewhat with the values found in stripping and pickup experiments. Finally, the DOM is modified to investigate two features (volume absorption that is asymmetric about the Fermi energy and zero absorption in the vicinity of the Fermi energy) that have been ignored in many DOM models. These modifications have little effect on the agreement of the calculations with the scattering data or with the bound-state quantities.