Uniform semiclassical and quantum calculations of Regge pole positions and residues for complex optical nuclear heavy-ion potentials

Abstract

The first uniform semiclassical (SC) calculations of Regge pole positions and residues have been carried out for four complex optical potentials, which have been used to fit [sup 16]O+[sup 28]Si elastic-scattering data at [ital E][sub lab]=55 MeV. In particular, we have extended a SC formalism developed for atomic and molecular scatterings to allow for the presence of a long-range Coulomb potential. The SC Regge poles and residues are compared with quantum results of Takemasa and Tamura [Phys. Rev. C 18, 1282 (1978)], who numerically integrated the radial Schroedinger equation. The SC computations show that Takemasa and Tamura missed ten poles. Using a modified version of the quantum computer code REGGE, due to Takemasa, Tamura, and Wolter [Comput. Phys. Commun. 18, 427 (1979)] we have located five of these poles---the remaining poles have residues of modulus [lt]10[sup [minus]8]. For low values of the Regge pole quantum number, [ital n], the SC and quantum pole positions are in close agreement, with larger differences for the residues. As [ital n] increases, the SC results become less accurate. However at high values of [ital n], the quantum results also lose accuracy due to numerical instabilities in the REGGE code. It is demonstrated that themore » choice of Coulomb interaction---charged sphere or pure Coulomb---can significantly effect the properties of the Regge pole positions and residues.« less