Nuclear orientation study of the decay of 171Lu

The levels and γ-ray transitions in 171Yb have been studied by radioactive decay of oriented 171Lu. The orientation was produced using the hyperfine field in ferromagnetic gadolinium to polarize an ensemble of 171Lu nuclei at a temperature of 14 mK. The directional distribution of the γ-rays was measured using high-resolution Ge(Li) detectors. Anisotropies of 30 γ-rays in 171Yb were measured. Multipole mixing ratios were deduced for most of the mixed γ-ray transitions and unambiguous spin assignments were made for several levels. The energy and structure of the rotational band levels, reduced E2 and M1 transition probalities and E2/M1 mixing ratios were calculated using the semi-microscopic quasiparticle-phonon model with a Coriolis interaction. In general, good agreement is obtained between the theoretical predictions and experimental results. (orig.)