Quadrupole-Octupole Collective States in the Light Actinides and the Spdf-Iba Model

A systematic study over a wide range of nuclei around Z ~ 88, N ~ 134, in terms of the spdf IBA model is presented. The variety of patterns of various properties of the lowest K = 0⁺ and K = 0^- are well described with only one negative parity boson. The disagreement on the behavior of the E1 matrix elements in ²26Ra at high spin (J ≥ 10) is interpreted as a signature for the onset of octupole deformation.