Resonance structure in the ${}_{}{}^{207}{}_{}{}^{}\mathrm{Pb}$ + n system has been investigated by measuring the neutron total cross section with high energy resolution and the partial radiative cross sections for transitions to the ground-state and the first-excited state in ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. A detailed analysis of resonance parameters was carried out up to a neutron energy of 700 keV. The nuclear level density shows a strong parity dependence. The doorway in the s-wave neutron strength function has been firmly established with an escape width equal to the corresponding widths in the neighboring isotopes. The total magnetic dipole strength detected between the neutron separation energy and 8.0 MeV is B(M1)↑=5.8 ${\mu }_{\mathrm{N}{}^2}$, thus smaller than the lowest theoretical estimate for that region. Above that energy an additional 1 ${\mu }_{\mathrm{N}{}^2}$ is observed, but more strength may have escaped detection because the sensitivity of the experiment decreases; thus the ‘‘missing’’ strength may be partly hidden at these higher energies. Radiative widths for the E1 decay of resonances to the first-excited state of ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ show a doorway structure which can be related to the properties of known bound states.

• Received 27 January 1987

DOI:https://doi.org/10.1103/PhysRevC.35.1646