α-decay Studies of the N=127 Isotones ²¹⁹U and ²¹⁶Ac

The light actinide nuclei ²¹⁹U and ²¹⁶Ac were produced in fusion-evaporation reaction using a ¹⁸³W target and ⁴⁰Ar beam. After recoiling from thin target, the fusion-evaporation residues were separated by the gas-filled recoil separator SHANS (Spectrometer for Heavy Atoms and Nuclear Structure) and transported into the focal plane detector systems, where their impantations and decays were measured. The method of searching for \alpha -decay chains was used to identify the nuclei. In this work, the known \alpha decay of ²¹⁹U was measured with improved precision and the \alpha -particle energy of 9 763(15) keV and a half-life of 60(7) μs was determined. In addition, two new \alpha -decay lines at 9 246(17) keV and 8 975(17) keV were observed and assigned as the decays from the ground state of ²¹⁹U to the (5/2 ^- ) and (3/2 ^- ) states of ²¹⁵Th, respectively. The existence of an \alpha -decaying isomeric state in ²¹⁶Ac was also confirmed.