Strong neutron pairing in core+4$n$ nuclei

A. Revel (1) , F.M. Marqués (2) , O. Sorlin (1) , T. Aumann , C. Caesar , M. Holl , V. Panin , M. Vandebrouck (3) , F. Wamers , H. Alvarez-Pol , L. Atar , V. Avdeichikov , S. Beceiro-Novo , D. Bemmerer , J. Benlliure , C.A. Bertulani , J.M. Boillos , K. Boretzky , M.J.G. Borge , M. Caamano , E. Casarejos , W.N. Catford , J. Cederkäll , M. Chartier , L. Chulkov , D. Cortina-Gil , E. Cravo , R. Crespo , U. Datta Pramanik , P. Fernandez Diaz , I. Dillmann , Z. Elekes , J. Enders , O. Ershova , A. Estrade , F. Farinon , L.M. Fraile , M. Freer , D. Galaviz , H. Geissel , R. Gernhauser , P. Golubev , K. Göbel , J. Hagdahl , T. Heftrich , M. Heil , M. Heine (4) , A. Heinz , A. Henriques , A. Hufnagel , A. Ignatov , H.T. Johansson , B. Jonson , J. Kahlbow , N. Kalantar-Nayestanaki , R. Kanungo , A. Kelic-Heil , A. Knyazev , T. Kroll , N. Kurz , M. Labiche , C. Langer , T. Le Bleis , R. Lemmon , S. Lindberg , J. Machado , J. Marganiec , A. Movsesyan , E. Nacher , M. Najafi , E. Nikolskii , T. Nilsson , C. Nociforo , S. Paschalis , A. Perea , M. Petri , S. Pietri , R. Plag , R. Reifarth , G. Ribeiro , C. Rigollet , M. Roder , D. Rossi , D. Savran , H. Scheit , H. Simon , I. Syndikus , J.T. Taylor , O. Tengblad , R. Thies , Y. Togano , P. Velho , V. Volkov , A. Wagner , H. Weick , C. Wheldon , G. Wilson , J.S. Winfield , P. Woods , D. Yakorev , M. Zhukov , A. Zilges , K. Zuber

1 GANIL - Grand Accélérateur National d'Ions Lourds
2 LPCC - Laboratoire de physique corpusculaire de Caen
3 IRFU - Institut de Recherches sur les lois Fondamentales de l'Univers
4 IPHC - Institut Pluridisciplinaire Hubert Curien

The emission of neutron pairs from the neutron-rich N=12 isotones C18 and O20 has been studied by high-energy nucleon knockout from N19 and O21 secondary beams, populating unbound states of the two isotones up to 15 MeV above their two-neutron emission thresholds. The analysis of triple fragment-n-n correlations shows that the decay N19(-1p)C18*→C16+n+n is clearly dominated by direct pair emission. The two-neutron correlation strength, the largest ever observed, suggests the predominance of a C14 core surrounded by four valence neutrons arranged in strongly correlated pairs. On the other hand, a significant competition of a sequential branch is found in the decay O21(-1n)O20*→O18+n+n, attributed to its formation through the knockout of a deeply bound neutron that breaks the O16 core and reduces the number of pairs.

Domaines: Physique Nucléaire Expérimentale [nucl-ex]

A. Revel, F.M. Marqués, O. Sorlin, T. Aumann, C. Caesar, et al.. Strong neutron pairing in core+4$n$ nuclei. Physical Review Letters, 2018, 120 (15), pp.152504. ⟨10.1103/PhysRevLett.120.152504⟩. ⟨hal-01737862⟩