Coexistence of Reflection Asymmetric and Symmetric Shapes in ^{144}Ba.

Level structures in the neutron-rich Ba-144 nucleus have been reinvestigated by measuring prompt gamma rays in the spontaneous fission of Cf-252. The previous s = +1 octupole band structure with reflection asymmetric shape has been expanded, and a side quadrupole band structure based on a 3+ state with reflection symmetric shape is identified. Thus, the results show the coexistence of reflection asymmetric and symmetric shapes in Ba-144. This is a first identification of such a shape coexistence structure in a nuclear structure. The other structural characteristics are discussed.