Multipole Admixtures of Transitions from Beta, Gamma, and Octupole Vibrational States inGd154

A NaI-Ge(Li) detector arrangement has been used to measure $\gamma -\gamma$ directional correlations in ${}_{}{}^{154}{}_{}{}^{}\mathrm{Gd}$ from the decay of ${}_{}{}^{154}{}_{}{}^{}\mathrm{Eu}$. From the NaI detector, gates were selected to span the 123-keV $2^{+}\to 0^{+}$, and 248-keV $4^{+}\to 2^{+}$ transition, and an equivalent region of the Compton distribution at 320 keV to obtain the background contribution to each gate. These gates opened 20488 channels of the memory of a 4096-channel analyzer for storage of data at 90, 135, and 180° from the Ge(Li) detector. The well-known 1274-123-keV and 873-123-keV correlations were used to obtain attenuation and Ge(Li) solid-angle corrections for cascades that involve the 123-keV $2^{+}$ state. The following correlations (in keV) were measured, with the $A_2$ and $A_4$ coefficients, respectively, in parentheses: 692-123, $2_{\beta }^{+}\to 2_g^{+}\to 0^{+}(-0.145\mathrm{}\pm 0.022,0.311\pm 0.040)$; 1005-123, $3_{\gamma }^{+}\to 2_g^{+}\to 0^{+}(-0.239\mathrm{}\pm 0.018$, -0.073 ± 0.026); 1494-123, $3^{-}\to 2_g^{+}\to 0^{+}(-0.075\mathrm{}\pm 0.029,-0.022\pm 0.044)$; 1597-123, $2^{-}\to 2_g^{+}\to 0^{+}(0.196\mathrm{}\pm 0.013$, -0.017 ± 0.021); 757-248, $3_{\gamma }^{+}\to 4_g^{+}\to 2_g^{+}(0.161\mathrm{}\pm 0.004$, -0.174 ± 0.006), 677-248, $4_{\beta }^{+}\to 4_g^{+}\to 2_g^{+}(-0.168\mathrm{}\pm 0.020,0.178\pm 0.029)$, 444-248, $2_{\beta }^{+}\to 4_g^{+}\to 0^{+}(0.196\mathrm{}\pm 0.009,0.095\pm 0.011)$; 625-248, $2_{\gamma }^{+}\to 4_g^{+}\to 2^{+}(0.187\mathrm{}\pm 0.014,0.108\pm 0.019)$; 893-248, $4_{\gamma }^{+}\to 4_g^{{}^{+}}\to 2^{+}(-0.037\mathrm{}\pm 0.010,0.160\pm 0.013)$; 881-248, $3^{-}\to 4_g^{+}\to 2^{+}(-0.132\mathrm{}\pm 0.058,-0.059\pm 0.086)$; 1188-248, $4^{-}\to 4_g^{+}\to 2^{+}(0.224\mathrm{}\pm 0.028,-0.010\pm 0.041)$; and 1246-248, $3^{-}\to 4_g^{+}\to 2^{+}(-0.151\mathrm{}\pm 0.007,0.010\pm 0.008)$. The following $M1\mathrm{}$ admixtures (in keV) were found in the transition from the $\beta$ and $\gamma$ bands: 692, $2_{\beta }^{+}\to 2_g^{+}\left({99.2}_{-0.7\mathrm{}}^{+0.3\mathrm{}}E2\right)$; 677, $4_{\beta }^{+}\to 4_g^{+}(>\mathrm{}80\%E2\mathrm{} \mathrm{for} 2\sigma \mathrm{limits})$; 1005, $3_{\gamma }^{+}\to 2_g^{+}\left({99.78}_{-0.23\mathrm{}}^{+0.20\mathrm{}}E2\right)$; 757, $3_{\gamma }^{+}\to 4_g(97.0\mathrm{}\pm 0.3\%E2)$; and 893, $4_{\gamma }^{+}\to 4_g^{+}(95.2\mathrm{}\pm 0.8\%E2)$. The transitions from the odd-parity states studied to the even-parity ground-state band are all 99.9 ± 0.1% $E1\mathrm{}$.