Low-spin indentical bands in neighboring odd-A and even-even nuclei: A challenge to mean-field theories.

A comprehensive study of odd-{ital A} rotational bands in normally deformed rare-earth nuclei indicates that a large number of seniority-one configurations (30% for odd-{ital Z} nuclei) at low spin have moments of inertia nearly identical to that of the seniority-zero configuration of the neighboring even-even nucleus with one less nucleon. It is difficult to reconcile these results with conventional models of nuclear pair correlation, which predict variations of about 15% in the moments of inertia of configurations differing by one unit in seniority.