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 $2_1^{+}$ state. The experimental branching ratios ${\mathit{R}}_{\exp }$=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 ${\mathit{R}}_{\exp }$ are in good agreement with the Alaga rules. Nevertheless, some branching ratios suggest a possible mixing of K values.

• Received 19 March 1990

DOI:https://doi.org/10.1103/PhysRevC.42.1945