Quadrupole deformed and octupole collective bands in 228Ra

Spins and parities for collective states in 228Ra have been determined from conversion electron measurements with a mini-orange β spectrometer. The fast-timing βγγ(t) method has been used to measure lifetimes of T12 = 550(20) ps and 181 (3) ps for the 21+ and 41+ aembers of the K = 0+ band, and T12 ⩽ 7 ps and ⩽6 ps for the 11− and 31− members of the K = 0− band, respectively The quadrupole moments, Q0 deduced from the B (E2; 21+ → 01+) and B (E2; 41+ → 21+) rates are in good agreement with the previously measured value and the systematics of the region. However, the B(E1) rates of ⩾4 × 10−4 e2 fm2, which represent the first B(E1) measurements for this nucleus, are at least 25 times larger than the value previously suggested for 228Ra. The new results are consistent with the B(E1) rates recently measured for the neighbouring 227Ra and reveal octupole correlations in 228Ra.