Production and decay properties of the lightest osmium isotopes

The production of Os 159 , 160 , 161 and Re 159 , 160 , 161 was investigated in experiments performed at the Accelerator Laboratory of the University of Jyväskylä. The nuclei of interest were produced using fusion-evaporation reactions induced by beams of 275–353 MeV Ni 58 ions bombarding a Cd 106 target. The evaporation residues were separated in flight using the recoil separator MARA and implanted into a double-sided silicon strip detector, which was used to measure their decays. Cross sections for the production of these nuclides were measured and the relative population of the 8 + isomeric states and ground states of the N =84 isotones Hf 156 , W 158 , and Os 160 were deduced. New decay chains assigned to Os 160 were identified at beam energies of 310 and 330 MeV. These findings are compared with previous studies claiming the observation of Os 160 and W 156 . The α decays of Os 161 were observed, confirming previous results for this nuclide and its β -decaying daughter, W 157 . The α -decay branch of Re 159 was also confirmed, but no delayed decays of this nuclide were observed that would be a signature of the β decays of the as yet unknown nuclide Os 159 .