Single-neutron states at high spins in ytterbium nuclei: Evidence for the quenching of static neutron pair correlations

Abstract

The decay schemes of 167,168,169Yb are established to the largest angular momenta yet known in stably-deformed rare-earth nuclei using the 124Sn( 48Ca,3–5n) reaction. The systematics of the resulting spectrum of single-neutron states in these and neighbouring Yb isotopes at large and small angular momenta are discussed with regard to that expected in the presence and absence of static neutron-pair correlations. This comparison, together with cranking-model and “gauge-space” analyses, provides evidence for the effective disappearance of static neutron-pair correlations for the odd- N isotopes at ħω ⩾ 0.38 MeV. A composite empirical spectrum of single-neutron states is constructed for the “unpaired” regime and is compared with cranking calculations.