New experimental limits on double-beta decay of osmium.

Double-beta processes in 184Os and 192Os were searched for over 15 851 h at the Gran Sasso National Laboratory (LNGS) of the I.N.F.N. by using a 118 g ultra-pure osmium sample installed on the endcap of a 112 cm3 ultra-low-background broad-energy germanium detector. New limits on double-electron capture and electron capture with positron emission in 184Os were set at the level of lim T1/2 ∼ 1016–1017 years. In particular the 2ν2K and 2νKL decays of 184Os to the ground state of 184W are restricted as T1/2 ⩾ 3.0 × 1016 years and T1/2 ⩾ 2.0 × 1016 years, respectively. A lower limit on the half-life for the double-beta decay of 192Os to the first excited level of 192Pt was set as lim T1/2 = 2.0 × 1020 years at 90% confidence level [ABSTRACT FROM AUTHOR]