Directional Correlation of Gamma Rays inGe72

Abstract

The $\gamma$ rays of ${}_{}{}^{72}{}_{}{}^{}\mathrm{Ge}$ following the $\beta$ decay of 14.1-h ${}_{}{}^{72}{}_{}{}^{}\mathrm{Ga}$ have been studied using a 20-${\mathrm{cm}}^3$ Ge(Li) detector in coincidence with a 2×2-in. NaI(Tl) crystal. Directional-correlation measurements have been carried out on the cascades involving 630-, 894-, 1231-, 2202-, 2491-, and 2508-keV $\gamma$ rays with the 834-keV groundstate transition from the first excited 2+ state. 1-3 directional-correlation measurements (with the intermediate $\gamma$ ray unobserved) have been made between $\gamma$ rays of energy 601, 786, 1000, 1051, 1215, 1597, and 1861 keV and the 834-keV transition. Spin assignments of 2 for the 1464- and the 3036-keV levels have been confirmed. The 630- and 2202-keV transitions are nearly pure $E2\mathrm{}$ and $E1\mathrm{}$, respectively. The level at 2065 keV has been assigned a spin of 3. The 601-keV transition has a maximum $M1\mathrm{}$ admixture of 10%. Assuming that the 2515-keV level is a 3- state, the following spin and mixing assignments can be made. The level at 1728 keV is found to have a spin of 4, which requires 0.4-1.3% octupole mixture in the 894-keV transition. The levels at 3325 and 3342 keV have been assigned spins of 3 and 2, respectively. The 786-, 1597-, 2491-, and 2508-keV transitions are all nearly pure $E1\mathrm{}$.