| The spectroscopy of the neutron-rich unbound system $^{7}$He has been investigated through high-energy neutron-removal from a $^{8}$He beam and coincident detection of the $^{6}$He charged fragment and neutron from the in-flight decay. Concerning the structure of $^{7}$He, there is a question as to the existence of an excited state (½-) 1 MeV above the $^{6}$He+n threshold. Experimentally, the $^{6}$He fragments were detected using a Si-Si-CsI telescope and the neutrons using the DEMON liquid scintillator array. From such a kinematically complete measurement it has been possible to reconstruct the $^{7}$He invariant mass spectrum. Preliminary analysis shows at present little or no evidence for any excited states. |
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