Relative 3s spectroscopic strength in 206Pb and 208Pb studied with the (e,e'p) knockout reaction.

A high-resolution ($e,{e}^{\ensuremath{'}}p$) measurement has been performed to determine the relative occupation probability of the $3{s}_{\frac{1}{2}}$ 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 $l=0$ knockout strength is observed in $^{205}\mathrm{Tl}$, whereas all $l=0$ 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 $^{208}\mathrm{Pb}$.