The mean lifetime of the $0_2^{}{}_{}{}^{+}$ state of ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$ is found to be 0.97 ± 0.10 nsec. This corresponds to a monopole strength $\rho =(2.6\mathrm{}\pm 0.3)\times {10}^{-2\mathrm{}}$ and $B(E2:{O_2}^{+}\to {2_1}^{+})<\mathrm{}2.0\mathrm{}{e}^2 {\mathrm{F}}^4$. The $E0$ strength can be accounted for with standard shell-model wave functions using a state-dependent monopole effective charge derived from isotope-shift data.

• Received 14 August 1972

DOI:https://doi.org/10.1103/PhysRevLett.29.878