Nuclear level repulsion and order vs. chaos

A statistical analysis of the distribution of level spacings for states with the same angular momentum and parity is described in which the average spacing is calculated for the total ensemble of states of given Iπ in even-even, odd-even, or even-odd nuclei. Though the resulting distribution of level spacings for states of deformed nuclei with Z = 62−75 and A = 155−185 is the closest to that of a Poisson distribution yet obtained for nuclear levels, significant deviations are observed for small level spacings. Such deviations are observed independent of spin, parity, nuclear type (even-even, even-odd, or odd-even), and intrinsic nuclear excitation. Many, but not all, of the very closely-spaced levels have K-values differing by several units.