NEUTRON-SCATTERING CROSS-SECTIONS FOR PB-204,206 NEUTRON AND PROTON AMPLITUDES OF E2 AND E3 EXCITATIONS

Differential elastic and inelastic scattering cross sections have been measured for neutrons incident on Pb-204 and Pb-206 at energies of 2. 5, 4.6, and 8.0 MeV and total cross sections in 100-keV steps from 250 keV to 4.0 MeV. Both spherical and coupled-channels analyses babe bee n used to interpret this large set of data, together with other total cross sections extending to 8 MeV. Several purposes motivate this work . The first is to establish the dispersion-corrected mean field approp riate-for these nuclei. ii consistent description of the energy depend ent neutron scattering potential includes a dispersion relation connec ting the real and imaginary parts of the potential; the resultant pote ntial relates the energy dependent scattering field to one representin g bound single particle levels. Dispersion relations using both the si ngle channel and coupled-channels models have been examined; both give very similar results. The second motivation is to deduce neutron and proton excitation strengths of the lowest-energy quadrupole and octupo le excitations seen via neutron scattering, and to compare those stren gths with similar values derived from electromagnetic excitation, heav y-ion and pion scattering. The role of target neutrons in both collect ive excitations was found to be enhanced compared to the proton role.