Sequential decay reactions induced by a 18 MeV He-6 beam on Li-6 and Li-7

摘要

The He-6 + Li-6 and He-6 + Li-7 reactions have been studied using a 18 MeV He-6 radioactive beam and a highly efficient and segmented detector set-up. Triple coincidence events corresponding to the He-6 + Li-6 → He-6 + α + d, He-6 + Li-6 → 2α + 1 + n and He-6 + Li-7 → He-6 + α + t reactions have been clearly observed. The dominant mechanism of these reactions has been found to be a sequential decay through the known cluster states in Li-6, Li-7, Be-8, Be-9 and Be-10. In particular, the sequential α-decay of the Be-10 state at E-x = 7.54 MeV has been observed although its decay energy is much smaller (130 keV) than the decay energy for neutron emission (730 keV). Furthermore, the Be-10 state at E-x ≈ 10.2 MeV has been found to be strongly populated in the reactions with both used targets. Angular correlations analysis of the events corresponding to the 10.2 MeV state α-decay suggests the 4(+) assignment. Both of these observations indicate a special, well-developed He-6 + α cluster structure of the Be-10 states involved. The structure of several low-lying 9Be states is also discussed. © 2005 Elsevier B.V. All rights reserved.