β-delayed deuteron emission from ⁶He

The β delayed deuteron decay of ⁶He has been measured at the TISOL facility at TRIUMF. For the β-particle measurement a silicon-germanium telescope array has been used. To separate deuterons from α particles and to obtain the spectral form of the deuteron decay, a d-α coincidence technique has been employed using two opposite silicon detectors. The β branch has been determined from the geometry of the experiment and also by comparison with the well-known β-α decay modes of ¹⁶N and ⁸Li. A branching ratio of (1.8±0.9) × 10^-6 above the β cutoff (350-kev deuteron laboratory energy) and (2.6±1.3) × 10^-6 for the entire ⁶ spectrum has been determined for this decay. In the course of the measurement the half-life of He has been remeasured to be T_1/2= 0.810±0.008 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.