New features of shape coexistence in Sm152

Excited states in Sm152 have been investigated with the Sm152(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 1681keV. This newly observed band has a remarkable similarity in its E1 transition rates for decay to the first excited Kπ=0+ band at 684keV 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 groundstate may indicate that Sm152 is a complex example of shape coexistence rather than a critical point nucleus. © 2009 The American Physical Society.