Damping of high-spin single-particle strengths inPb209

The stripping reaction (α,${\mathrm{}}^3$He) at 183 MeV incident energy has been used to study the neutron-particle response function on a ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ target nucleus up to 15 MeV excitation energy. Detailed spectroscopic information has been obtained on the low-lying neutron states (0–4 MeV) through angular distribution measurements and standard distorted wave Born approximation analysis. A large enhancement of cross section is observed between 5 and 15 MeV. It appears as a broad bump superimposed on a continuous background which has been analyzed within the framework of the plane wave breakup model. The excitation energies, angular distributions, and strengths of these high-lying transitions suggest that they arise from neutron stripping to high-spin outer subshells, i.e., 2$h_{11/2}$, 1$k_{17/2}$, and 1$j_{13/2}$ in ${}_{}{}^{209}{}_{}{}^{}\mathrm{Pb}$. The results are compared with predictions from the core-particle model and from the quasiparticle-phonon model.