Decay ofHf181

Abstract

The decay of ${\mathrm{Hf}}^{181}$ to ${\mathrm{Ta}}^{181}$ was studied by angular correlation measurements ($133K\ensuremath{-}482\ensuremath{\gamma}$, $133\ensuremath{\gamma}\ensuremath{-}482\ensuremath{\gamma}$, and $133\ensuremath{\gamma}\ensuremath{-}482K$, energies being given in kev), conversion coefficient measurements [${\ensuremath{\alpha}}_{K}(133)=0.50\ifmmode\pm\else\textpm\fi{}0.06$, ${\ensuremath{\alpha}}_{K}(136)=1.2\ifmmode\pm\else\textpm\fi{}0.2$, ${\ensuremath{\alpha}}_{K}(346)=0.038\ifmmode\pm\else\textpm\fi{}0.007$, ${\ensuremath{\alpha}}_{K}(482)=0.023\ifmmode\pm\else\textpm\fi{}0.002$], $\frac{K}{L}$ ratios, and coincidence measurements. The weak 137-kev transition, first observed by Mihelich, was placed in the decay by delayed coincidence measurements. The spin assignments are in excellent agreement with the calculations of Nilsson on the strong-coupling model. Comparison of $K\ensuremath{-}\ensuremath{\gamma}$ and $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ correlation coefficients in the Hf${\mathrm{O}}_{2}$ sources fails to show any after effects of $K$-hole formation on the correlation coefficients. The discrepancy between the $\frac{E2}{M1}$ ratio obtained from $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ correlation measurements and conversion coefficient measurements in the 482-kev transition is discussed in terms of the improved finite nuclear size corrections to $M1$ conversion coefficients described by Church and Weneser.