Statistical investigation of factors affecting rotational motion in even-even nuclei

The distribution of rotational energy spacings for low-spin yrast states in over two thousand pairs of deformed rare-earth even-even nuclei are studied to determine key factors that correlate with the moments of inertia. Nuclei with near identical P values (P=NpNn/[Np+Nn] where Np and Nn are the numbers of valence protons and valence neutrons) are more than an order of magnitude more likely to show near identical bands than nuclei with different P values. This is, by far, the highest correlation found: no other variable is even 20% as effective. The statistical significance of these large P enhancements and the special relation between P and ground-state mean-field structures is confirmed by a complementary analysis of negative parity near identical bands, which show no P enhancement at all