First Results of a $^{8}$He+d Experiment
Résumé
Secondary 8He beam delivered by the fragment separator ACCULINNA was used in an experiment designed for the simultaneous study of the 7H and 9He exotic nuclei. Attempt to observe 7H produced in the reaction 2H(8He,3He)7H resulted only in setting a cross section limit, d$\$sigma/d$\Omega$ < 20 µb/sr, for the reaction channel which could populate a resonance lying between 0 and 3 MeV above the 7H decay threshold. The spectrum of 9He was studied by means of the 2H(8He,p)9He reaction. Energy and angular correlations were obtained for the 9He decay products by complete kinematical reconstruction. The lowest resonant state of 9He is found at about 2 MeV with a width of ~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+ (a limit of a0 > −20 fm on the scattering length is obtained), and with a $5/2^+$ resonance located at ~4.2 MeV.