Observation of Bound-State beta - Decay of Fully Ionized 187Re: 187Re-187Os Cosmochronometry.

We observed the bound-state ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay of fully ionized ${}^{187}$Re nuclei circulating in a storage ring. With two independent methods the time dependent growth of hydrogenlike ${}^{187}$Os ions has been measured and a half-life of $32.9\ifmmode\pm\else\textpm\fi{}2.0\mathrm{yr}$ for bare ${}^{187}$Re nuclei could be determined, to be compared with 42 Gyr for neutral ${}^{187}$Re atoms. With the resulting $\mathrm{log}\mathrm{ft}$ value of $7.87\ifmmode\pm\else\textpm\fi{}0.03$ the half-life of ${}^{187}$Re ions in any ionization state can be calculated. Thus one can correct the ${}^{187}$Re${\ensuremath{-}}^{187}$Os galactic chronometer calibration, by taking account of the ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay enhancement in stellar interiors, which will lead to a more accurate estimate of the galactic age.