First observation of alpha decay of 190-Pt to the first excited level   (E_{exc}=137.2 keV) of 186-Os
  The alpha decays of naturally occurring platinum isotopes, which are accompanied by the emission of gamma quanta, have been searched for deep underground (3600 m w.e.) in the Gran Sasso National Laboratories of the INFN (Italy). A sample of Pt with mass of 42.5 g and a natural isotopic composition has been measured with a low background HP Ge detector (468 cm^3) during 1815 h. The alpha decay of 190-Pt to the first excited level of 186-Os (J^\pi = 2^+, E_{exc}=137.2 keV) has been observed for the first time, with the half-life determined as: T_{1/2} = 2.6_{-0.3}^{+0.4} (stat.) \pm 0.6 (syst.) \times 10^{14} yr. The T_{1/2} limits for the alpha decays of other Pt isotopes have been determined at level of T_{1/2} \simeq 10^{16}-10^{20} yr. These limits have been set for the first time or they are better than those known from earlier experiments. 
P. Belli (1), R. Bernabei (1,2), F. Cappella (3,4), R. Cerulli (5),   F.A. Danevich (6), A. Incicchitti (3), M. Laubenstein ...
nucl-ex