The observation of nuclear shape transitions at fixed angular momentum

Abstract

Abstract The low temperature behaviour of 24Mg for fixed values of the angular momentum is examined in both the finite temperature mean field approximation and the canonical ensemble. The canonical ensemble calculations provide evidence that the shape transitions predicted by mean field calculations do occur. In both calculations the shape transitions result in a peak in the specific heat and a corresponding sudden increase in the many-body energy level density and we conclude that a relevant order parameter for these transitions is a function of the latter quantity. In addition, the results indicate that shape transitions are due to the thermal excitation from collective to non-collective portions of the nuclear energy eigenspectrum. This appears to be a general result, and should also apply to shape transitions in heavier nuclei.