M1Admixtures of Transitions inGd156

Abstract

$\gamma -\gamma$ directional-correlation measurements were carried out with a NaI-Ge(Li) detector system on the transitions in ${}_{}{}^{156}{}_{}{}^{}\mathrm{Gd}$ whose levels are populated from the decay of ${}_{}{}^{156}{}_{}{}^{}\mathrm{Eu}$. Directional correlations of the 88.95-keV $\gamma$ ray with 11 transitions which directly feed and 4 which involve a skipped transition to the 88.95-keV state were simultaneously measured. A $\delta$ value of ${-5.9\mathrm{}}_{-2.8\mathrm{}}^{+1.4\mathrm{}}$ was measured for the 1040.44-keV, $2_{\beta }^{+}\to 2_g^{+}$ transition which is thus (${97.2}_{-2.1\mathrm{}}^{+1.5\mathrm{}}$)% $E2\mathrm{}$. The 1065.14-keV, $2_{\gamma }^{+}\to 2_g^{+}$ transition has a $\delta =-18\mathrm{}\pm 3$ and a (99.7 ± 0.1)% $E2\mathrm{}$ component. Three $1^{+}\to 2_g^{+}$ transitions of 1877.03, 1937.71, and 2097.70 keV have $E2\mathrm{}$ admixtures of (${13.8}_{-2.9\mathrm{}}^{+3.0\mathrm{}}$), (${24.5}_{-1.9\mathrm{}}^{+2.0\mathrm{}}$), and (${59.0}_{-9.0\mathrm{}}^{+25.2\mathrm{}}$)%, respectively, while the 811.77-keV, $1^{+}\to 2_{\gamma }^{+}$ transition is (${0.1}_{-0.1\mathrm{}}^{+0.4\mathrm{}}$)% $E2\mathrm{}$.