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

TL;DR

This study reports the first observation of alpha decay of 190-Pt to the first excited level of 186-Os, with a measured half-life, using deep underground gamma spectroscopy of platinum samples.

Contribution

First detection of alpha decay of 190-Pt to an excited state, with precise half-life measurement and improved limits for other platinum isotopes.

Findings

First observation of 190-Pt alpha decay to excited state

Half-life measured as approximately 2.6 x 10^14 years

Set new limits on alpha decay half-lives of other Pt isotopes

Abstract

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.