Gamma-gamma directional correlation studies with two Ge (Li) detectors were performed on transitions in ${}_{}{}^{156}{}_{}{}^{}\mathrm{Gd}$ from the decay of ${}_{}{}^{156}{}_{}{}^{}\mathrm{Eu}$. Seventeen correlations were measured including four one-three correlations. The $2^{+}-2_g^{+}$ transitions from $K^{\pi }=0^{+}$ states at 1129 and 1258 keV have strikingly different $E2\mathrm{}$ admixtures of >99.7% and ${12.6}_{-2.8\mathrm{}}^{+3.6\mathrm{}}$, respectively. The results for other one-two correlations are $(E\gamma ,I_i,\% \mathrm{admixture}\mathrm{of}\mathrm{the}\mathrm{first}\mathrm{transition}):(1065,2\mathrm{}\gamma ,E2={99.7}_{-0.5\mathrm{}}^{+0.3\mathrm{}}),(1154,1,M2={0.01}_{-0.01\mathrm{}}^{+0.08\mathrm{}}),(1231,2,M2<0.18),(1277,1,M2<0.06), (1857,1,\sigma 1>92.7), (1877,1,E2={9.3}_{-2.5\mathrm{}}^{+2.7\mathrm{}}), (1938,1,E2=28\mathrm{}\pm 2), (2098,1,E2={68}_{-8\mathrm{}}^{+9\mathrm{}}), \mathrm{and} (2181,1,E2={30}_{-4\mathrm{}}^{+5\mathrm{}})$. For the one-three correlations one obtains $(E\gamma ,I_i-I,\% \mathrm{admixture}\mathrm{of}\mathrm{the}\mathrm{first}\mathrm{transition}):(812,1\mathrm{}-2,E2={0.57}_{-0.32\mathrm{}}^{+0.42\mathrm{}}),(867,1\mathrm{}-2,M2<7.2),(944,1-1,M2<3.8), \mathrm{and} (970,2\mathrm{}-4,E2>98.6)$. The experimental branching ratios for the 1258 keV second $K^{\pi }I=0^{+}2$ state are in marked disagreement with the Bohr-Mottleson predictions after corrections for the 80% $M1\mathrm{}$ admixture in the 2-2 transition. The results of this work and those of previous works have been compared and the averaged results are reported in the text.

RADIOACTIVITY ${}_{}{}^{156}{}_{}{}^{}\mathrm{Gd}$; measured $\gamma -\gamma \left(\theta \right)$; deduced $\delta$, $B\left(E2\mathrm{}\right)\mathrm{}$ ratios.

• Received 24 January 1977

DOI:https://doi.org/10.1103/PhysRevC.16.2019