Nuclear spectroscopic studies of 252Es

Abstract

The decay scheme of 252Es has been investigated with high-resolution semiconductor detectors in conjunction with coincidence techniques. The half-life of 252Es was measured by following the decay of the α-count rate associated with 252Es decay and was found to be 350±50 d. The electron capture and α-decay branchings were measured to be (22±2)% and (78±6)%, respectively. The EC decay almost entirely populates a level at 969.8 keV in 252Cf with a log ft value of 8.9. This state has been identified as the two-neutron state n[613] 7 2 +; n[620] 1 2 +3 + . A K π = 2 − band has been identified at 830.8 keV. A rotational band built on an 804.8 keV level has been interpreted as the γ-vibrational band ( K π = 2 +). On the basis of the observed log ft value, the ground state of 252Es has been given an assignment of {n[613] 7 2 +; p[521] 3 2 −5 − . The favored α-transition of 252Es has been found to populate a level at 590 keV in 248Bk. The ground state of 248Bk has been given a spin-parity assignment of 6 + with the twoquasiparticle configuration n[734] 9 2 −; p[521] 3 2 − .