Empirical evidence for coriolis coupling of octupole states in 172Yb

The nucleus 172Yb has been studied using the (3He, α) and (d, t) reactions on targets of 173Yb. Beams of 12 MeV deuterons and 24 MeV 3He particles were obtained from the McMaster FN Tandem Van de Graaff accelerator and the reaction products were analysed with a magnetic spectrograph. The (3He, α) reaction was particularly useful in identifying states formed by coupling the 72+ [633] transferred neutron to the 52− [512] target ground state. The Kπ = 1− coupling of these orbitals makes up a large fraction of the Kπ = 1− octupole vibration, which was found to be strongly perturbed by Coriolis coupling with other octupole states. The most striking feature is that Coriolis coupling with the Kπ = 0− octupole band, which has only odd-spin rotational members, produces a significant odd-even shift in the rotational spacing of the Kπ = 1− band. These results are in excellent agreement with the predictions of Neerg.ard and Vogel. The observation of the Kπ = 6∼, 72+[633] + 52−[512] rotational band up to spin I = 9 confirmed the previous assignment for the bandhead of this configuration to the isomeric state at 1551 keV. The Kπ = 3+ and Kπ = 8+, case112− [505] ± case52−[512], two-neutron configurations have also been identified in the present work. In addition, several other new assignments have been tentatively proposed.