Fine Structure in the alpha decays of ²²⁶U and ²³⁰Pu

Abstract:

The nuclei ²²⁶U and ²³⁰Pu have been populated via reactions involving ²⁰⁸Pb targets bombarded by ²²Ne and ²⁶Mg projectiles. Fusion-evaporation residues were separated in-flight using a gas-filled recoil separator. A position-sensitive Si-strip detector was employed at the focal plane in order to identify correlated α-decay chains. Two fine structure α-decay lines have been observed. The first, with an energy of 7385(5) keV, is assigned as the α decay from ²²⁶U to the first excited 2⁺ state of ²²²Th. The second line, observed for the first time in this work, has an energy of 6961(30) keV and is assigned as the α decay from ²³⁰Pu to the first excited 2⁺ state of ²²⁶U. The excitation energy of the first excited 2⁺ state in ²²⁶U was determined to be 96(25) keV, giving an estimate of the deformation parameter β₂≃ 0.20.