Decay of an isomeric state in Cm²⁴⁴

Abstract

The 1042 keV state in Cm²⁴⁴, which is populated in the β^--decay of 10.1 Am²⁴⁴ has previously been assigned (K, Iπ)=(6,6⁺). This assignment has now been confirmed through an angular correlation measurement, and it was found that the 746 keV γ-ray is a mixture of 46% quadrupole (E2) and 54% dipole (M1). The half life of the 1042 keV state has been determined by measurement of delayed coincidences between β-particles and conversion electrons. The result is 34±2 ms. Comparison with the single particle estimate shows that the E2 transitions from the delayed state are hindered by factors of about 10¹⁰. This reflects the fact that the transitions are four times forbidden in K. The relative transition probabilities for the E2's from the delayed state are shown to agree well with a recent theoretical estimate.