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 T _1/2 = 3.6(2) min and the (1^-) state with T_1/2 = 2.9(2) min. The 1185.5 keV level in ²³⁶Pu was found to be the K isomer with K^π = 5^- and t_1/2 = 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 K^π = 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.