The distribution of nuclear quantum states in cold'' rotating nuclei

A statistical analysis of the distribution of level spacings for states with the same spin and parity is described in which the average spacing is calculated for the total ensemble. The resulting distribution of level spacings for states of deformed nuclei with A = 155--185 and Z = 62--77 is the closest to that of a Poisson distribution yet obtained for nuclear levels. However, when only the even-spin, positive-parity data for even-even nuclei are considered, the level-spacing distribution becomes double peaked. The anomalously-large separations are shown to be the result of the low energy of the strongly-correlated, completely-paired yrast configuration of even-even nuclei. Average values of the level spacings also are discussed as a function of spin, parity, and nuclear type (even-even, even-Z- odd-N, etc.). Likewise, deviations from a Poisson distribution for several spacings (s) less than about 60 keV are compared with similar values for {sup 116}Sn on an absolute scale. Such discrepancies are attributed to interactions (level repulsions) which become increasingly significant for s {le} 60 keV. 18 refs., 10 figs