The 8He and 10He spectra studied in the (t,p)(t,p) reaction

The low-lying spectra of 8He and 10He nuclei were studied in the 3H(6He, p)8He and 3H(8He, p)10He transfer reactions. The 0+0+ ground state (g.s.) of 8He and excited states, 2+2+ at 3.6–3.9 MeV3.6–3.9 MeV and (1+)(1+) at 5.3–5.5 MeV5.3–5.5 MeV, were populated with cross sections of 200, 100–250, and 90–125 μb/sr, respectively. Some evidence for a 8He state at about 7.5 MeV was obtained. We discuss a possible nature of the near-threshold anomaly above 2.14 MeV in 8He and relate it to the population of a 1−1− continuum (soft dipole excitation) with a peak value at about 3 MeV. The lowest energy group of events in the 10He spectrum was observed at ∼3 MeV with a cross section of ∼140 μb/sr∼140 μb/sr. We argue that this result is consistent with the previously reported observation of 10He providing the new 10He g.s. position at about 3 MeV.