Abstract
Measurements of the internal conversion electron spectrum and the identification of EO transitions linking the excited O+ states in 172Yb provide new information on the level structure of this nucleus. The (n,e-) reaction with a Yb2O3 target enriched in 171Yb was used and all possible EO transitions were searched for. Several new low-energy EO transitions were observed and evidence was found for a new 0+ level at 1920 keV. This may be due to pair excitation, which is also a possible explanation for the 1405 keV 0+ level. The authors show that an alternative explanation for the 1405 keV level is that it is the head of a Kpi =0+ mixed symmetry band with band members at 1477 keV (2+) and 1633 keV (4+). The level energies, B(E2) values, multipole mixing ratios and X values are compared with the predictions of the DDM and the IBA-2.