New Features of Shape Coexistence in 152Sm

Excited states in 152Sm have been investigated with the 152Sm(n,n'γ) reaction. The lowest four negative-parity band structures have been characterized in detail with respect to their absolute decay properties. Specifically, a new Kπ=0- band has been assigned with its 1- band head at 1681 keV. This newly observed band has a remarkable similarity in its E1 transition rates for decay to the first excited Kπ=0+ band at 684 keV to the lowest Kπ=0- band and its decay to the ground-state band. Based on these decay properties, as well as energy considerations, this new band is assigned as a Kπ=0- octupole excitation based on the Kπ=02+ state. An emerging pattern of repeating excitations built on the 02+ level similar to those built on the ground state may indicate that 152Sm is a complex example of shape coexistence rather than a critical point nucleus.