The quadrupole coupling constant of the $\pi {\left(h_{\frac{11}{2}}^{-1\mathrm{}} s_{\frac{1}{2}}^{-1\mathrm{}}\right)}_{5^{-}}$ isomer in polycrystalline ${}_{}{}^{206}{}_{}{}^{}\mathrm{Hg}$ at 225 K has been measured by means of the perturbed angular distribution method. The result is $\frac{e^2\mathrm{Qq}}{h}=136.5\mathrm{}\pm 3$ MHz, from which we deduce $eQ=65\mathrm{}\pm 13 e$ ${\mathrm{fm}}^2$ and an effective charge $e_{\mathrm{eff}}\left(\pi h_{\frac{11}{2}}^{-1\mathrm{}}\right)=(2.2\mathrm{}\pm 0.5)e$.

• Received 17 July 1984

DOI:https://doi.org/10.1103/PhysRevC.30.1702