First search for double-β decay of platinum by ultra-low background HP Ge γ spectrometry

A search for double-beta processes in (190)Pt and (198)Pt was realized with the help of ultra-low background HP Ge 468cm(3) gamma spectrometer in the underground Gran Sasso National Laboratories of the INFN (Italy). After 1815 h of data taking with 42.5 g platinum sample, T(1/2) limits on 2 beta processes in (190)Pt (epsilon beta(+) and 2 epsilon) have been established on the level of 10(14)-10(16) y, 3 to 4 orders of magnitude higher than those known previously. In particular, a possible resonant double-electron capture in (190)Pt was restricted on the level of 2.9 x 10(16) y at 90% C. L. In addition, T(1/2) limit on 2 beta(-) decay of (198)Pt (2 nu + 0 nu) to the 2(1)(+) excited level of (198)Hg has been set at the first time: T(1/2) > 3.5 x 10(18) y. The radiopurity level of the used platinum sample is reported.