β-delayed deuteron emission from6He

The \ensuremath{\beta} delayed deuteron decay of ${}^{6}\mathrm{He}$ has been measured at the TISOL facility at TRIUMF. For the \ensuremath{\beta}-particle measurement a silicon-germanium telescope array has been used. To separate deuterons from $\ensuremath{\alpha}$ particles and to obtain the spectral form of the deuteron decay, a $d\ensuremath{-}\ensuremath{\alpha}$ coincidence technique has been employed using two opposite silicon detectors. The \ensuremath{\beta} branch has been determined from the geometry of the experiment and also by comparison with the well-known $\ensuremath{\beta}\ensuremath{-}\ensuremath{\alpha}$ decay modes of ${}^{16}\mathrm{N}$ and ${}^{8}\mathrm{Li}.$ A branching ratio of $(1.8\ifmmode\pm\else\textpm\fi{}0.9)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ above the $\ensuremath{\beta}$ cutoff (350-keV deuteron laboratory energy) and $(2.6\ifmmode\pm\else\textpm\fi{}1.3)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ for the entire spectrum has been determined for this decay. In the course of the measurement the half-life of ${}^{6}\mathrm{He}$ has been remeasured to be ${T}_{1/2}=0.810\ifmmode\pm\else\textpm\fi{}0.008 \mathrm{s}.$ High statistical accuracy in the deuteron spectrum has been obtained that allowed a comparison of the shape of the deuteron spectrum to theoretical predictions.