Experimental evidence for subshell closure in He-8 and indication of a resonant state in He-7 below 1 MeV
Skaza, F Lapoux, V Keeley, N Alamanos, N Pollacco, EC Auger, F Drouart, A Gillibert, A Beaumel, D Becheva, E Blumenfeld, Y Delaunay, F Giot, L Kemper, KW Nalpas, L Obertelli, A Pakou, A Raabe, Riccardo Roussel-Chomaz, P Sida, JL Scarpaci, JA Stepantsov, S Wolski, R
American physical soc
Physical Review C vol:73 issue:4 pages:-
The spectroscopy of the unstable He-8 and unbound He-7 nuclei is investigated via the p(He-8, d) transfer reaction with a 15.7A MeV He-8 beam from the SPIRAL facility. The emitted deuterons were detected by the telescope array MUST. The results are analyzed within the coupled-channels Born approximation framework, and a spectroscopic factor (CS)-S-2=4.4 +/- 1.3 for neutron pickup to the He-7(g.s.) is deduced. This value is consistent with a full p3/2 subshell for He-8. Tentative evidence for the first excited state of He-7 is found at E-*=0.9 +/- 0.5 MeV (width Gamma=1.0 +/- 0.9 MeV). The second one is observed at a position compatible with previous measurements, E-*=2.9 +/- 0.1 MeV. Both are in agreement with previous separate measurements. The reproduction of the first excited state below 1 MeV would be a challenge for the most sophisticated nuclear theories.