Properties of low-lying 9He state

The spectrum of 9He was studied by means of the 8He(d,p)9He 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 9He decay products by complete kinematical reconstruction. The data analysis was done in the assumption of a direct one-neutron transfer reaction mechanism. The 9He structure was analysed in the framework of a simple single-particle model. The lowest resonant state of 9He is found at about 2?MeV with a width of ?2MeV 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+(a limit on the scattering length is obtained as a > -20fm), and with a 5/2+resonance at energy ?4.2MeV.