Uncommon decay branching ratios of spin-one states in the rare-earth region and evidence for K mixing

In nuclear resonance fluorescence (NRF) measurements of well deformed rare-earth nuclei we observe for most of the excited J=1 levels of both parities the ground-state transition and the corresponding transition to the 21+ state. The experimental branching ratios Rexp=B(1→2)/B(1→0) are compared with the predictions of the Alaga rules. The examination of 171 levels found in NRF experiments yields that most values of Rexp are in good agreement with the Alaga rules. Nevertheless, some branching ratios suggest a possible mixing of K values