Symmetric and antisymmetric states: A general feature of two-component systems.

It is shown that in both the nuclear shell model, considering explicitly proton and neutron degrees of freedom (seniority scheme), and in particle-core coupling model calculations, 2/sup +/ levels with symmetric and antisymmetric character in the constituent unperturbed basis result. Besides the excitation energy for such 2/sup +/ levels, the E2 decay properties also are studied. Constructive and destructive interference between the two distinct E2 matrix elements results for the 2/sub 1//sup +/ (symmetric) and 2/sub 2//sup +/ (antisymmetric) levels, respectively. Applications are shown for the Cd (Z = 48) and the N = 84 nuclei.