Structure of 13Be studied in proton knockout from 14B

Structure of 13Be studied in proton knockout from 14B

Ribeiro, G.; Nacher, E.; Tengblad, O.; Diaz Fernandez, P.; Aksyutina, Y.; Alvarez-Pol, H.; Atar, L.; Aumann, T.; Avdeichikov, V.; Beceiro-Novo, S.; Bemmerer, D.; Benlliure, J.; Bertulani, C. A.; Boillos, J. M.; Boretzky, K.; Borge, M. J. G.; Caamano, M.; Caesar, C.; Casarejos, E.; Catford, W.; Cederkall, J.; Chartier, M.; Chulkov, L.; Cortina-Gil, D.; Cravo, E.; Crespo, R.; Datta Pramanik, U.; Dillmann, I.; Elekes, Z.; Enders, J.; Ershova, O.; Estrade, A.; Farinon, F.; Fraile, L. M.; Freer, M.; Fynbo, H. O. U.; Galaviz, D.; Geissel, H.; Gernhäuser, R.; Golubev, P.; Göbel, K.; Hagdahl, J.; Heftrich, T.; Heil, M.; Heine, M.; Heinz, A.; Henriques, A.; Holl, M.; Hufnagel, A.; Ignatov, A.; Johansson, H. T.; Jonson, B.; Kalantar-Nayestanaki, N.; Kanungo, R.; Kelic-Heil, A.; Kurz, N.; Kröll, T.; Labiche, M.; Langer, C.; Le Bleis, T.; Lemmon, R.; Lindberg, S.; Machado, J.; Marganiec, J.; Movsesyan, A.; Nilsson, T.; Nociforo, C.; Panin, V.; Paschalis, S.; Perea, A.; Petri, M.; Pietri, S.; Plag, R.; Reifarth, R.; Rigollet, C.; Riisager, K.; Rossi, D.; Röder, M.; Savran, D.; Scheit, H.; Simon, H.; Sorlin, O.; Syndikus, I.; Taylor, J. T.; Thies, R.; Velho, P.; Wagner, A.; Wamers, F.; Vandebrouck, M.; Weick, H.; Wheldon, C.; Wilson, G.; Wimmer, C.; Winfield, J. S.; Woods, P.; Zhukov, M. V.; Zilges, A.; Zuber, K.

The neutron-unbound isotope 13Be has been studied in several experiments using different reactions, different projectile energies and different experimental setups. There is, however, no real consensus in the interpretation of the data, in particular concerning the structure of the low-lying excited states. Gathering new experimental information, which may reveal the 13Be structure, is a challenge, in particular in light of its bridging role between 12Be, where the N=8 neutron-shell breaks down, and the Borromean halo nucleus 14Be. The purpose of the present study is to investigate the role of bound excited states in the reaction product 12Be after proton knockout from 14B, by measuring coincidences between 12Be, neutrons, and rays originating from de-excitation of states fed by neutron decay of 13Be. The 13Be isotopes were produced in proton-knockout from a 400 MeV/u 14B beam impinging on a CH2 target. The 12Be-n relative-energy spectrum dsigma=dEfn was obtained from coincidences between 12Be(g.s.) and a neutron, and also as threefold coincidences by adding rays, from the de-excitation of excited states in 12Be. Neutron decay from the first 5=2+ state in 13Be to the 2+ state in 12Be at 2.11 MeV is cofirmed. An energy-independence of the proton-knockout mechanism is found from a comparison with data taken with a 35 MeV/u 14B beam. A low-lying p-wave resonance in 13Be(1/2+) is confirmed by comparing proton- and neutron-knockout data from 14B and 14Be.

Keywords: radioactive beams; nuclear structure; unbound nuclei; 13Be

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