Pb206+nresonances forE=600−900keV: Neutron strength functions

Data from high resolution neutron transmission and differential scattering measurements performed on ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$ have been analyzed for $E=600-900\mathrm{}$ keV. Resonance parameters (i.e., $E$, $l$, $J$, and ${\Gamma }_n$) have been deduced for many of the 161 resonances observed. Strength functions and potential phase shifts for $s$-, $p$-, and $d$-wave neutrons for $E_n-0-900\mathrm{}$ keV are compared with optical model calculations. It is found that the phase contributed by the external $R$ function as well as the integrated neutron strength functions can be reproduced for the $s$ and $d$ waves with a well depth of $V_0=50.4\mathrm{}$ MeV for the real potential and $W_D=6.0\mathrm{}$ MeV for an imaginary surface potential. Somewhat smaller values ($V_0=48.7\mathrm{}$ MeV and $W_D=2.0\mathrm{}$ MeV) are required to reproduce the $p$-wave data. These values of the real potential are also found to give the experimentally observed binding energies for the $4s_{\frac{1}{2}}$, $3d_{\frac{3}{2}}$, and $3d_{\frac{5}{2}}$ single particle levels ($V_0=50.4\mathrm{}$ MeV), and the $3p_{\frac{1}{2}}$ single particle level ($V_0=48.7\mathrm{}$ MeV). Nuclear level densities for $s$ and $d$ waves are found to be well represented by a constant temperature model. However, the model under estimates the number of $p$-wave resonances.