α decay of Re159 and proton emission from Ta155

Abstract

The α decay of Re159 has been observed for the first time in reactions of 300 MeV Ni58 ions with an isotopically enriched Cd106 target. The Re159 ions were separated in-flight using the RITU separator and implanted into the GREAT spectrometer. The α decay emanates from the proton-emitting πh11/2 state in Re159 with an energy of Eα=6776±26 keV and a branching ratio of 7.5 ± 3.5%. This α decay populates a state in the closed neutron shell nucleus Ta155, which decays by emitting 1444 ± 15 keV protons with a half-life of 2.9-1.1+1.5 ms. These values are consistent with the emission of the proton from a πh11/2 orbital. These results fit in with the systematics of proton and α-particle separation energies in the region, but disagree with the previously reported decay properties of Ta155. © 2007 The American Physical Society.