Observation of K=1/2 octupole deformed bands in ²²⁷Th

High-spin states in ²²⁷Th have been populated using the reaction ²²⁶Ra(α,3n)²²⁷Th at a bombarding energy of 33 MeV. The high-spin rotational structures of this nucleus have been refined and extended. In addition, the linking of these structures with the low-spin states known from ²³¹U α decay has allowed a comprehensive decay scheme of this nucleus to be assembled for the first time. Four previously known rotational bands are interpreted as Coriolis coupled K^π=1/2⁺ and K^π=1/2^- bands, in agreement with predictions using a reflection-asymmetric mean field approach. The determination of decoupling parameters for these bands is consistent with the a(K^π=1/2⁺)=-a(K^π=1/2^-) rigid octupole rotor expectation. A further rotational band is interpreted as having K^π=3/2^-. Measured D₀/Q₀ ratios are consistent with an interpolation of the values given for neighboring even-even nuclei, providing further evidence for the significance of strong octupole correlations in this nucleus.