Role of inelastic couplings in ⁴He + ²⁰⁸Pb elastic scattering in a wide energy range

Abstract

The phenomenological strengths of the real part of the optical potential, obtained from elastic scattering data analyses within the optical model approach, present significant energy-dependence. This behavior has been associated to the intrinsic energy-dependence of the effective nucleon-nucleon interaction. However, in earlier works, we proposed that at least part of this dependence can arise from the effect of couplings to inelastic states of the nuclei. In order to deepen this study, in this paper we present extensive data analyses for the elastic scattering and inelastic excitation of 111 states of 208Pb, for the 4He + 208Pb system in a wide energy range. With the purpose of comparison, the theoretical cross sections are obtained in different approaches for the imaginary part of the potential, and within both contexts: optical model (distorted wave Born approximation) and coupled-channel calculations.