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Physical Review C 76 (2007) 021605
New insight into the low-energy $^{9}$He spectrum
M.S. Golovkov, L.V. Grigorenko, A.S. Fomichev, A.V. Gorshkov, V.A. Gorshkov, S.A. Krupko, Yu.Ts. Oganessian, A.M. Rodin, S.I. Sidorchuk, R.S. Slepnev, S.V. Stepantsov, G.M. Ter-Akopian, R. Wolski, A.A. Korsheninnikov, E.Yu. Nikolskii, V.A. Kuzmin, B.G. Novatskii, D.N. Stepanov, S. Fortier1, P. Roussel-Chomaz2, W. Mittig2

The spectrum of $^9$He was studied by means of the $^8$He($d$,$p$)$^9$He reaction at a lab energy of 25 MeV/n and small center of mass (c.m.) angles. Energy and angular correlations were obtained for the $^9$He decay products by complete kinematical reconstruction. The data do not show narrow states at $\sim $1.3 and $\sim $2.4 MeV reported before for $^9$He. The lowest resonant state of $^9$He is found at about 2 MeV with a width of $\sim $2 MeV and is identified as $1/2^-$. The observed angular correlation pattern is uniquely explained by the interference of the $1/2^-$ resonance with a virtual state $1/2^+$ (limit on the scattering length is obtained as $a > -20$ fm), and with the $5/2^+$ resonance at energy $\geq 4.2$ MeV.
1 :  IPNO - Institut de Physique Nucléaire d'Orsay
2 :  GANIL - Grand Accélérateur National d'Ions Lourds
Physique/Physique Nucléaire Expérimentale
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