Unresolved Question of the 10He Ground State Resonance
The ground state of 10He was populated using a 2p2n-removal reaction from a 59 MeV/u 14Be beam. The decay energy of the three-body system, 8He+n+n, was measured and a resonance was observed at E=1.60(25) MeV with a 1.8(4) MeV width. This result is in agreement with previous invariant mass spectroscopy measurements, using the 11Li(-p) reaction, but is inconsistent with recent transfer reaction results. The proposed explanation that the difference, about 500 keV, is due to the effect of the extended halo nature of 11Li in the one-proton knockout reaction is no longer valid as the present work demonstrates that the discrepancy between the transfer reaction results persists despite using a very different reaction mechanism, 14Be(-2p2n).