Structure with the lowest energy observed in the 10He spectrum populated
in the proton knockout reaction with 11Li beam has a peak at 1.2β1.5
MeV. This peak is usually interpreted as a resonant 0+ ground state of
10He. Our theoretical calculations indicate that this peak is likely to be
a pileup of 1β, 0+, and 2+ excitations with very similar shapes. %We
predict a very specific nature of the 1β excitation in 10He. Moreover,
the ``soft'' 1β excitation appears to be the lowest one in energy. Such an
anomalous continuum response is traced to the halo structure of 11Li
providing extreme low energy shift to all the expected continuum excitations.
Competitions of the initial state structure (ISS) and the final state
interaction (FSI) effects on the spectrum and three-body correlations in
10He are discussed. Analogous effect of the extreme low-energy shift could
also be expected in other cases of 2n emitters populated in reactions with
halo nuclei. Simplified example of the 10He spectrum in Ξ± knockout
from 14Be, is given. We also discuss limits on the properties of 9He
stemming from the observed 10He spectrum.Comment: 10 pages, 13 figure
