Observation of unstable superheavy hydrogen isotope 6H in the 7Li(7Li, 8B) reaction

A broad maximum associated with the formation of the 6H unstable nucleus is observed in the spectrum of the 8Be nuclei from the 7Li(7Li, 8B) reaction at Esub(sup(7)Li)=82 MeV. The 6H mass defect is measured to be 41.99+-0.4 MeV, which means that the 6H nucleus is unstable relative to the decay 6H → 3H+3n, the instability value being of 2.7+-0.4 MeV. The 6H decay width is GITA=1.8+-0.5 MeV. Detection of 6H is of interest because a nuclear system with such a high ratio of the number of neutrons to protons: Nsub(n)/Nsub(p)=5 has been observed for the first time. The second important result is that the 6H nucleus turned out to be more stable than the 4H; the binding energy is equal to 2.7 MeV for 6H and 3.4 MeV for 4H. In this respect the 4H-6H nuclei behave just as ''anomalous'' 5He-7He and 6He-8He nuclei whose stability grows with the addition of a pair of neutrons