Experimental evidence for subshell closure in {sup 8}He and indication of a resonant state in {sup 7}He below 1 MeV

• Published in: Physical review. C, Nuclear physics Nuclear physics, 2006-04, Vol.73 (4)
• Main Authors: Skaza, F., Lapoux, V., Keeley, N., Alamanos, N., Pollacco, E. C., Auger, F., Drouart, A., Gillibert, A., Nalpas, L., Obertelli, A., Raabe, R., Sida, J.-L., Beaumel, D., Becheva, E., Blumenfeld, Y., Delaunay, F., Scarpaci, J.-A., Giot, L., Roussel-Chomaz, P., Kemper, K. W.
• Format: Article
• Language: English
• Subjects: BORN APPROXIMATION; COUPLED CHANNEL THEORY; DEUTERONS; EXCITED STATES; HELIUM 7; HELIUM 8; ION EMISSION; MEV RANGE; NEUTRONS; NUCLEAR PHYSICS AND RADIATION PHYSICS; NUCLEAR THEORY; SPECTROSCOPIC FACTORS; TRANSFER REACTIONS
• ISSN: 0556-2813; 1089-490X
• DOI: 10.1103/PhysRevC.73.044301

The spectroscopy of the unstable {sup 8}He and unbound {sup 7}He nuclei is investigated via the p({sup 8}He, d) transfer reaction with a 15.7A MeV {sup 8}He 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 C{sup 2}S=4.4{+-}1.3 for neutron pickup to the {sup 7}He{sub g.s.} is deduced. This value is consistent with a full p3/2 subshell for {sup 8}He. Tentative evidence for the first excited state of {sup 7}He is found at E{sup *}=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{sup *}=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.