Global systematics of the Wigner energy

Following Zeldes, double-beta decay Q values are used as a filter for extracting symmetry energy and Wigner energy coefficients across the full range of nuclei, from A = 10 to A = 246. The symmetry coefficient extracted is found to vary smoothly with A and mass formula coefficients can be determined for the corresponding symmetry and surface symmetry terms. However, the extracted Wigner coefficient has large standard errors and fluctuates dramatically with A, even as regards its sign. Shell corrections remove most of the fluctuations and allow the determination of a reliable Wigner coefficient for the mass formula. (C) 2008 Elsevier B.V. All rights reserved.