New Experimental Limits On Double-Beta Decay Of Osmium

Double-beta processes in Os-184 and Os-192 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 cm(3) ultra-low-background broad-energy germanium detector. New limits on double-electron capture and electron capture with positron emission in Os-184 were set at the level of lim T (1/2) similar to 10(16)-10(17) years. In particular the 2 nu 2K and 2 nu KL decays of Os-184 to the ground state of W-184 are restricted as T (1/2) > 3.0 x 10(16) years and T (1/2) > 2.0 x 10(16) years, respectively. A lower limit on the half-life for the double-beta decay of Os-192 to the first excited level of Pt-192 was set as lim T (1/2) = 2.0 x 10(20) years at 90% confidence level