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International Symposium on Exotic Nuclei, Khanty-Mansiysk : Russie, Fédération De (2006)
Search for resonances in $^4$n, $^7$H and $^9$He via transfer reactions
S. Fortier1, E. Tryggestad1, E. Rich1, D. Beaumel1, E. Becheva1, Y. Blumenfeld1, F. Delaunay1, A. Drouart2, A. Fomichev, N. Frascaria1, S. Gales3, L. Gaudefroy3, A. Gillibert2, J. Guillot1, F. Hammache1, K. W. Kemper, E. Khan1, V. Lapoux2, V. Lima1, L. Nalpas2, A. Obertelli2, E. C. Pollacco2, F. Skaza2, U. Datta Pramanik, P. Roussel-Chomaz3, D. Santonocito, J. A. Scarpaci1, O. Sorlin3, S. V. Stepantsov, G. M. Ter Akopian, R. Wolski
SPIRAL Collaboration(s)

Investigation of unbound nuclear systems 9He, 7H and 4n was performed at GANIL-SPIRAL using the 8He beam at 15.3 A MeV and a CD2 target. The missing mass spectra were deduced from kinetic energies and emission angles of light ejectiles detected by the Silicon array MUST. In addition to previously known low-lying narrow resonant states in 9He, the d(8He,p) reaction displays a structure just above neutron emission threshold, identified with the “true” ground state of 9He. The analysis of angular distributions shows that the inversion of s1/2 and p1/2 neutron shells previously observed in 11Be and 10Li also exists in the lightest N=7 isotone 9He. The d(8He,3He) and d(8He,6Li) reactions were used to search for resonant states in the t+4n (7H) and 4n systems, respectively. The missing mass spectrum of the 4n system does not give evidence for the existence of a bound “tetraneutron”. However the comparison with the results of 5-body phase-space calculations emphasizes the existence of correlations in the 4n system. The broad structure observed at ~=2 MeV above the t+4n emission threshold is proposed to be the ground state of 7H
1 :  IPNO - Institut de Physique Nucléaire d'Orsay
2 :  DAPNIA - Département d'Astrophysique, de physique des Particules, de physique Nucléaire et de l'Instrumentation Associée
3 :  GANIL - Grand Accélérateur National d'Ions Lourds
Physique/Physique Nucléaire Expérimentale
nuclei with mass number 6 to 19 – hydrogen – helium – neutrons – nuclear resonances