Electromagnetic transitions in multiple chiral doublet bands

Multiple chiral doublet bands (M chi D) in the 80, 130 and 190 mass regions are studied by the model of gamma=90 degrees triaxial rotor coupled with identical symmetric proton-neutron configurations. By selecting a suitable basis, the calculated wave functions are explicitly exhibited to be symmetric under the operator A, which is defined as rotation by 90 degrees about the 3-axis with the exchange of valance proton and neutron. We found that both M1 and E2 transitions are allowed between levels with different values of A, while they are forbidden between levels with same values of A. Such a selection rule holds true for MxD in different mass regions.