Beta-Gamma Spectroscopy Of The Os-195 Nucleus

The beta-gamma spectroscopy of Os-195 nucleus was performed at the KEK isotope separation system (KISS). The radioactive isotope of Os-195 was produced by the multinucleon transfer reactions of Xe-136 beams and Pt-198 target. The isotope of interest was separated and extracted by using KISS, which is an argon-gas-cell based laser ion source with a mass separator. Those extracted isotopes are implanted into an aluminized mylar tape, which is surrounded by the multisegmented proportional gas counter (MSPGC) and four clover-type high-purity germanium (HPGe) detectors for the beta-gamma spectroscopy. 27 gamma-ray peaks were observed in coincidence with internal conversion electrons and x rays detected by the MSPGC. 21 of them were identified as beta-delayed gamma rays of the Os-195 ground state, where the energies of 19 gamma-ray peaks agree with the literature values of transitions observed in Ir-195(n, gamma) reactions and two gamma-ray peaks were newly found. The beta-decay branching ratios of the Os-195 ground state were deduced. The obtained log-ft values range from 5.99(4) to 7.56( 22), indicating all beta-decay channels are the first forbidden transitions. It suggests that the spin-parity of the Os-195 ground state is 3/2(-), which is consistent with the systematical expectation. The beta-decay half-life of the Os-195 ground state was evaluated to be 6.5(4) min, which agrees well to the previously known value 6.5(11) min.