β decay of 6He into the α+d continuum

The rare β-decay channel of 6He into the α+d continuum was investigated at the REX-ISOLDE facility. Bunches of postaccelerated 6He ions were implanted into the optical time projection chamber (OTPC), where the decays with emission of charged particles were recorded. This novel technique allowed us to extend the low-energy end of the spectrum down to 150 keV in α+d center of mass, corresponding to a deuteron energy of 100 keV. The branching ratio for this process amounts to [2.78±0.07(stat)±0.17(sys)]×10^{−6}. The shape of the spectrum is found to be in a good agreement with a three-body model, while the total intensity is about 20% larger than the predicted one.We would like to thank the ISOLDE facility for providing the excellent beam. We are grateful to P. Descouvemont for providing us with the results of Ref. [15] in a tabular form. The work was partially supported by the Polish National Science Center under Contract No. UMO-2011/01/B/ST2/01943, by the European Nuclear Science and Applications Research (ENSAR) under Project No. 262010, by the Research Foundation - Flanders (FWO), by GOA/2010/010 (BOF KU Leuven), and by the Interuniversity Attraction Poles Programme initiated by the Belgian Science Policy Office (BriX network P7/12)