Relative3sSpectroscopic Strength inPb206andPb208Studied with the (e,e′p) Knockout Reaction

A high-resolution ($e,e^{\prime }p$) measurement has been performed to determine the relative occupation probability of the $3s_{\frac{1}{2}}$ proton orbits in ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$ and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. The knockout strength to the ground state of ${}_{}{}^{205}{}_{}{}^{}\mathrm{Tl}$ is 31(3)% smaller than that of ${}_{}{}^{207}{}_{}{}^{}\mathrm{Tl}$. Appreciable fragmentation of $l=0\mathrm{}$ knockout strength is observed in ${}_{}{}^{205}{}_{}{}^{}\mathrm{Tl}$, whereas all $l=0\mathrm{}$ strength in the excitation range up to 5.5 MeV resides in the ground state of ${}_{}{}^{207}{}_{}{}^{}\mathrm{Tl}$. Up to this energy the summed $3s$ strength is found to be 16(9)% smaller in ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$ than in ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$.