Neutron decay from the giant resonance region in 208Pb.

Abstract

The neutron decay of the giant multipole resonance region from 9 to 15 MeV of excitation energy in $^{208}\mathrm{Pb}$ has been studied. Neutron branching ratios for the decay to the ground state or to the low-lying excited states of $^{207}\mathrm{Pb}$ were measured as a function of the excitation energy of $^{208}\mathrm{Pb}$ and compared to Hauser-Feshbach calculations. While the neutron branching ratios from the isoscalar quadrupole resonance are reproduced by the calculations, the ratios from excitation energies above 12.5 MeV show a large excess with respect to the statistical predictions.