The Directional Correlation of thePb204γ−γCascade

Abstract

The directional correlation of the ${\mathrm{Pb}}^{204}$ $\gamma -\gamma$ cascade has been measured in chemical compounds and in a liquid Pb-Tl alloy. The values for the anisotropy of the ${\mathrm{Pb}}^{204}$ cascade in the chemical compounds vary between 0.08±0.04 and 0.46±0.04, thus showing a pronounced influence of extranuclear fields. The anisotropy in the liquid Pb-Tl alloy, 0.49±0.05, excludes the assignment $7^{-}$ for the second excited state of ${\mathrm{Pb}}^{204}$. The only decay scheme compatible with all experimental data requires the assignments $2^{+}$ and $6^{+}$ to the first and second state, respectively. The first $\gamma$ transition in ${\mathrm{Pb}}^{204}$ must be a mixture of approximately 90 percent $E4\mathrm{}$ and 10 percent $M5\mathrm{}$.