A measurement of $B\left(E3\mathrm{}\right)$ in the two-proton nuclide ${}^{134}\mathrm{Te}$ was made, giving the first empirical value of the effective proton octupole charge in the neutron rich doubly closed shell region at ${}^{132}\mathrm{Sn}$. It is demonstrated that the effective $E2\mathrm{}$ and $E3\mathrm{}$ charges can be used to derive the core phonon strengths in ${}^{132}\mathrm{Sn}$ and ${}^{208}\mathrm{Pb}$. The octupole charge and the corresponding phonon strength were found to be substantially lower at ${}^{132}\mathrm{Sn}$ than at ${}^{208}\mathrm{Pb}$, thus confirming long standing theoretical predictions of a weak octupole collectivity in the heavy Sn region.

• Received 10 April 1995

DOI:https://doi.org/10.1103/PhysRevLett.75.3090