Multipole mixing ratios of transitions in ¹⁵⁴Gd

The authors have measured gamma gamma and e_K- gamma directional correlations and the gamma ray directional distributions from oriented nuclei to determine the multipole mixing ratios of most prominent gamma ray transitions in ¹⁵⁴Gd and the angular momentum change in the Delta pi , yes gamma decays from ¹⁵⁴Eu which have large ft values. The analysis showed that the Delta pi , yes 3^- to 2⁺ and 3^- to 4⁺ transitions with log ft>10 are pure Delta J_beta =1 while the 3^- to 3⁺ beta decay to the 1127 keV level, log ft=10.7, has at least 60% Delta J_beta =0. They found that the gamma ray mixing ratios were approximately constant for the group of transitions linking the gamma and ground-state bands. They also obtained the E0:E2 internal conversion amplitude ratio of the 873.2 keV 2_gamma ⁺ to 2_GS⁺ transition. The particle parameters describing internal conversion were evaluated for the 123.1 and 247.9 keV transitions and are consistent with theory. Results are compared with values derived from the dynamic deformation theory based on the pairing-plus-quadrupole model and from band-mixing calculations and also with calculated values based on the interacting boson model.