Direct Evidence for Octupole Deformation in ^146Ba and the Origin of Large E1 Moment Variations in Reflection-Asymmetric Nuclei

Despite the more than one order of magnitude difference between the measured dipole moments in ^144Ba and ^146Ba, the strength of the octupole correlations in ^146Ba are found to be as strong as those in ^144Ba with a similarly large value of B(E3;3^- → 0^+) determined as 48(^+21_-29) W.u. The new results not only establish unambiguously the presence of a region of octupole deformation centered on these neutron-rich Ba isotopes, but also manifest the dependence of the electric dipole moments on the occupancy of different neutron orbitals in nuclei with enhanced octupole strength, as revealed by fully microscopic calculations.