Quenched E1 transition rates in Th-231

The fast timing beta gamma gamma(t) method has been used to measure lifetimes of the low-lying levels in Th-231 populated in the beta(-) decay of Ac-231. The half-life of the K-pi = 5/2(-) band-head at 185.7-keV was measured as T-1/2 = 1073(79) ps, yieldi
Addresses: Aas AJ, Univ Oslo, Dept Chem, POB 1033, N-0315 Oslo, Norway. Univ Oslo, Dept Chem, N-0315 Oslo, Norway. Uppsala Univ, Dept Neutron Res, S-61182 Nykoping, Sweden. Charles Univ, Dept Nucl Phys, CR-18000 Prague, Czech Republic. CSIC, Inst Estructu