Further Test ofM1Admixtures in the Decay of2+′ Beta Vibrational States

Abstract

The $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ directional correlation of the 692-123 keV, ${2}^{+}$\ensuremath{'} \ensuremath{\rightarrow} ${2}^{+}$ \ensuremath{\rightarrow} ${0}^{+}$ cascade in $^{154}\mathrm{Gd}$ was remeasured with an improved Ge(Li)-NaI system. The spectra in coincidence with the Compton background and the 123-keV photopeak were simultaneously recorded at each angle. The new results averaged with our earlier work yield ${A}_{2}=\ensuremath{-}0.141\ifmmode\pm\else\textpm\fi{}0.022$ and ${A}_{4}=0.311\ifmmode\pm\else\textpm\fi{}0.040$. These values are consistent only with the 692-keV transition being essentially pure $E2$.