We have developed a new method to study the order-to-chaos transition in rotational nuclei. Correlations between successive $\gamma$ rays are used to determine the average complexity of the intermediate levels and thereby the ratio of the interaction potential between levels to the level spacing. The measured ratios, 0.15 to 1.5, span the range from nearly fully ordered to nearly fully chaotic.

• Received 3 May 2004

DOI:https://doi.org/10.1103/PhysRevLett.94.042501