Regular versus chaotic dynamics in nuclear spectra near the ground state

In an attempt to determine wether the low-lying parts of nuclear spectra are regular or chaotic, we analyse a recent set of data on low-lying levels in nuclei ranging from 24Na to 244Am. We evaluate the nearest-neighbour spacing distribution and the Δ3 statistic. We find strong indications for regularity in rotational-like states in even-even nuclei, and some evidence that natural parity states in odd-odd nuclei are not completely chaotic. The other states in both types of nuclei seem to have statistical distributions which are consistent with complete chaoticity. (orig.)