Statistical Fluctuations of Electromagnetic Transition Intensities and Electromagnetic Moments in pf-Shell Nuclei

We study the fluctuation properties ofT = 0 electromagnetic transition intensities and electromagnetic moments in A ∼ 60 nuclei within the frame- work of the interacting shell model, using a realistic effective interaction for pf-shell nuclei with a 56 Ni core. The distributions of the transition intensities and of the electromagnetic moments are well described by the Gaussian or- thogonal ensemble of random matrices. In particular, the transition intensity distributions follow a Porter-Thomas distribution. When diagonal matrix ele- ments (i.e., moments) are included in the analysis of transition intensities, we find that the distributions remain Porter-Thomas except for the isoscalar M1. The latter deviation is explained in terms of the structure of the isoscalar M1 operator.