Spectroscopy of the highly neutron-deficient N=84 isotones 160Os and 159Re

Abstract

Neutron deficient N=84 isotones have been synthesised in 106Cd (58Ni) fusion evaporation reactions in an experiment performed at the University of Jyvaskyla accelerator laboratory. Reaction products were identified and their properties measured using the GREAT spectrometer in conjunction with the RITU gas- filled separator and the LISA spectrometer, while the Jurogam II spectrometer was used to measure gamma rays emitted at the target position. Mother-daughter correlations have been used to produce evidence for the first observation of alpha decay from the ground state of 160Os. The Q-value and half-life of the signal were measured to be 7415 (50) keV and 35 +19 -15 us, respectively. No evidence of the expected 8+ isomer was found. Further experimental work at the University of Jyvaskyla has been approved on the strength of this work. Improved measurements of the decay properties of h11/2 state in 159Re and 155Ta have been performed. The half-life of this state in 159Re was measured to be 21(1) us. The decay energy and branching ratios were 6818(6) keV and 5.0(8)% for the alpha decay branch and 1802(5) keV and 95(4) % for the proton decay branch. The proton decay of 155Ta was measured to have an energy of 1429(5) keV and a half-life of 3.3(6) ms. All values are consistent with previous works. Gamma rays above the h11/2 state in 159Re were identified for the first time and comparisons to the odd-Z isotone 157Ta were used to deduce the order of the lowest lying of these gamma rays. Evidence for the expected alpha-decaying 25/2- isomer was found.