Analyzing power measurements for 209Bi(n,n) at 6 and 9 MeV and consistent dispersive optical-model analyses for n+209Bi and n+208Pb from -20 to +80 MeV.

Abstract

High-accuracy measurements of ${\mathit{A}}_{\mathit{y}}$(\ensuremath{\theta}) data for elastic scattering for n${+}^{209}$Bi have been performed at 6 and 9 MeV. The data are incorporated into a large database of \ensuremath{\sigma}(\ensuremath{\theta}), ${\mathit{A}}_{\mathit{y}}$(\ensuremath{\theta}), and ${\mathrm{\ensuremath{\sigma}}}_{\mathit{T}}$ for n${+}^{209}$Bi covering the energy range 1.0--80 MeV. A complementary database is constructed for n${+}^{208}$Pb and a dispersive optical-model analysis is performed for both scattering systems while constraining many of the parameters to be identical for both systems. A good representation of both databases is obtained with conventional geometry and spin-orbit parameters. The $^{208}\mathrm{Pb}$ model predicts quite well the measured energies of valence single-particle and single-hole bound states. Occupation probabilities and spectroscopic factors for the same bound states are also calculated. Finally, a fully constrained model is presented in which the only differences between the n${+}^{208}$Pb and the n${+}^{209}$Bi systems are the Fermi energy and the isospin dependence in the real volume potential. \textcopyright{} 1996 The American Physical Society.