Beyond the neutron drip line: The unbound oxygen isotopes $^{25}$O and $^{26}$O

C. Caesar , J. Simonis , T. Adachi , Y. Aksyutina , J. Alcantara , S. Altstadt , H. Alvarez-Pol , N. Ashwood , T. Aumann , V. Avdeichikov , M. Barr , S. Beceiro , D. Bemmerer , J. Benlliure , C.A. Bertulani , K. Boretzky , M.J.G. Borge , G. Burgunder (1) , M. Caamano , E. Casarejos , W. Catford , J. Cederkall , S. Chakraborty , M. Chartier , L. Chulkov , D. Cortina-Gil , U. Datta Pramanik , P. Diaz Fernandez , I. Dillmann , Z. Elekes , J. Enders , O. Ershova , A. Estrade , F. Farinon , L. M. Fraile , M. Freer , M. Freudenberger , H.O U. Fynbo , D. Galaviz , H. Geissel , R. Gernhauser , P. Golubev , D. Gonzalez Diaz , J. Hagdahl , T. Heftrich , M. Heil , M. Heine , A. Heinz , A. Henriques , M. Holl , J.D. Holt , G. Ickert , A. Ignatov , B. Jakobsson , H.T. Johansson , B. Jonson , N. Kalantar-Nayestanaki , R. Kanungo , A. Kelic-Heil , R. Knöbel , T. Kröll , R. Krucken , J. Kurcewicz , M. Labiche , C. Langer , T. Le Bleis , R. Lemmon , O. Lepyoshkina , S. Lindberg , J. Machado , J. Marganiec , V. Maroussov , J. Menendez , M. Mostazo , A. Movsesyan , A. Najafi , T. Nilsson , C. Nociforo , V. Panin , A. Perea , S. Pietri , R. Plag , A. Prochazka , A. Rahaman , G. Rastrepina , R. Reifarth , G. Ribeiro , M. V. Ricciardi , C. Rigollet , K. Riisager , M. Röder , D. Rossi , J. Sanchez del Rio , D. Savran , H. Scheit , A. Schwenk , H. Simon , O. Sorlin (1) , V. Stoica , B. Streicher , James Taylor , O. Tengblad , S. Terashima , R. Thies , Y. Togano , E. Uberseder , J. van de Walle , P. Velho , V. Volkov , A. Wagner , F. Wamers , H. Weick , M. Weigand , C. Wheldon , G. Wilson , C. Wimmer , J.S. Winfield , P. Woods , D. Yakorev , M.V. Zhukov , A. Zilges , M. Zoric , K. Zuber

1 GANIL - Grand Accélérateur National d'Ions Lourds

The very neutron-rich oxygen isotopes 25O and 26O are investigated experimentally and theoretically. The unbound states are populated in an experiment performed at the R3B-LAND setup at GSI via proton-knockout reactions from 26F and 27F at relativistic energies around 442 and 414 MeV/nucleon, respectively. From the kinematically complete measurement of the decay into 24O plus one or two neutrons, the 25O ground-state energy and width are determined, and upper limits for the 26O ground-state energy and lifetime are extracted. In addition, the results provide indications for an excited state in 26O at around 4MeV. The experimental findings are compared to theoretical shell-model calculations based on chiral two- and three-nucleon (3N) forces, including for the first time residual 3N forces, which are shown to be amplified as valence neutrons are added.

Domaines: Physique Nucléaire Expérimentale [nucl-ex]

C. Caesar, J. Simonis, T. Adachi, Y. Aksyutina, J. Alcantara, et al.. Beyond the neutron drip line: The unbound oxygen isotopes $^{25}$O and $^{26}$O. Physical Review C, 2013, 88, pp.034313. ⟨10.1103/PhysRevC.88.034313⟩. ⟨in2p3-00862732⟩