Properties of very n-rich He isotopes

Abstract : Low-energy spectra of the 8,10He nuclei were investigated in the (t, p)-type reactions at small centre-of-mass angles using ∼ 25AMeV beams of 6He and 8He nuclei. The 0+ ground state (g.s.) of 8He and excited states, 2+ at 3.6-3.9MeV and (1+) at 5.3-5.5MeV, were populated with cross-sections of 200, 100-250, and 90-125 μb/sr, respectively. To account for a near-threshold anomaly observed in the 8He spectrum the population of a 1− continuum (soft dipole excitation) was considered. The lowest-energy group of events in the 10He spectrum was observed at ∼ 3MeV with a cross-section of ∼ 140 μb/sr. This result is consistent with the previously reported observation of 10He providing a new g.s. position for 10He at about 3MeV.