Three band crossings in the yrast structure of 162Hf

The yrast sequence of 162Hf has been observed up to a level tentatively assigned as 38+ and reveals a continuing rotational character up to that spin. Sharp backbends at rotational frequencies of 0.27 and 0.42 MeV/h are attributed to i13/2 neutron and h11/2 proton alignments, respectively. A gradual increase in the aligned angular momentum of the yrast levels between these two sharp backbends is attributed to the rotational alignment of a pair of negative parity quasineutrons (mostly h9/2 in character). The interpretation of this effect is supported by the failure of the negative parity bands, which already contain this aligned h9/2 neutron, to gain alignment in the same rotational frequency range. While the alignment of the h9/2 quasineutrons has been predicted in the cranked shell model to occur in the rare-earth region with a large interaction strength, this represents the first clear observation of such a band crossing.

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