Isomerism in theN=81isotopeDy147

Abstract

With the use of a helium-gas-jet capillary transport system a new (59±3)-sec activity was observed in ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ bombardments of ${}_{}{}^{141}{}_{}{}^{}\mathrm{Pr}$. The activity was found to be associated with two coincident $\gamma$ rays, 72.0 ± 0.1 and 678.7 ± 0.2 KeV. The 678.7-keV transition was also observed to be in coincidence with dysprosium $K$ x rays and its yield as a function of bombarding energy varied in the same manner as $\gamma$ rays known to follow the decay of 1.9-min ${}_{}{}^{147}{}_{}{}^{}\mathrm{Tb}$. From these results we conclude that the new activity is ${}_{}{}^{147}{}_{}{}^{}\mathrm{Dy}_{}^m{}_{}{}^{}$ and that the 72.0- and 678.7-keV $\gamma$ rays represent transitions in ${}_{}{}^{147}{}_{}{}^{}\mathrm{Dy}$. Further, based on the systematic behavior of low-lying levels in $N=81\mathrm{}$ odd-$A$ nuclei, we propose that our data establish the $h_{\frac{11}{2}}$ and $d_{\frac{3}{2}}$ neutron states in ${}_{}{}^{147}{}_{}{}^{}\mathrm{Dy}$ to be 750.7 and 72.0 keV, respectively, above the $s_{\frac{1}{2}}$ ground state.