arXiv 1102.25452011-02-13nucl-ex

First observation of alpha decay of 190-Pt to the first excited level (E_{exc}=137.2 keV) of 186-Os

P. Belli, R. Bernabei, F. Cappella, R. Cerulli, F. A. Danevich, A. Incicchitti, M. Laubenstein, S. S. Nagorny, S. Nisi, O. G. Polischuk, V. I. Tretyak

备注：: 12 pages, 3 figures, accepted for publication on Phys. Rev. C
发表信息：: Phys.Rev.C83:034603,2011
DOI：: 10.1103/PhysRevC.83.034603

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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^π= 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.

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