Magnetic form factors of /sup 205/Tl and /sup 207/Pb: Establishing the limits of mean-field theory

The ground-state magnetization densities of /sup 207/Pb and /sup 205/Tl have been studied by 180/sup 0/ elastic electron scattering. The magnetic form factors were found to be quenched substantially relative to the predictions of the independent-particle model. Microscopic calculations indicate that core polarization can account for part of the observed suppression but it is not sufficient to reproduce the data. The quenching observed at high momentum transfers is comparable to that observed in related electron-scattering studies in the lead region, and can be explained in terms of partial occupancy of shell orbits in /sup 208/Pb.