Proton-neutron configurations in 236g, mAm and its EC-decay daughter 236Pu

The EC decay of 236Am has been studied using a gas-jet coupled on-line isotope separator. A half-life analysis revealed that there are two EC-decaying states in 236Am: the 5- state with T1/2 = 3.6(2) min and the (1-) state with T1/2 = 2.9(2) min. The 1185.5 keV level in 236Pu was found to be the K isomer with Kπ = 5- and t1/2 = 1.2(3) μs. EC transitions from 236g, mAm to the 1185.5, 1311.5, and 1340.8 keV levels in 236Pu show small log ft values of 4.9, 5.3, and 4.8, respectively, indicating that the π5/2+[642] → ν5/2+[633] transition largely contributes to these transitions, and thus, the populated levels should be the π5/2-[523]π5/2+[642] two-quasiparticle states. The Kπ = 0- octupole band established in 236Pu is located at higher energy than those in 238,240Pu, which implies that the octupole correlations become weak at 236Pu.