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arXiv · 1803.04777

Strong neutron pairing in core+4n nuclei

A. Revel·F. M. Marques·O. Sorlin·T. Aumann·C. Caesar·M. Holl·V. Panin·M. Vandebrouck·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. Diaz Fernandez·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·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
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Abstract

The emission of neutron pairs from the neutron-rich $N\!=\!12$ isotones $^{18}$C and $^{20}$O has been studied by high-energy nucleon knockout from $^{19}$N and $^{21}$O 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 $^{19}$N$(-1p)^{18}$C$^*\!\rightarrow^{16}$C+$n$+$n$ is clearly dominated by direct pair emission. The two-neutron correlation strength, the largest ever observed, suggests the predominance of a $^{14}$C 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 $^{21}$O$(-1n)^{20}$O$^*\!\rightarrow^{18}$O+$n$+$n$, attributed to its formation through the knockout of a deeply-bound neutron that breaks the $^{16}$O core and reduces the number of pairs.

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A. Revel, F. M. Marques, O. Sorlin, T. Aumann, C. Caesar, M. Holl, V. Panin, M. Vandebrouck, 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. Diaz Fernandez, 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, 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. 2018-03-13. Strong neutron pairing in core+4n nuclei. https://doi.org/10.1103/physrevlett.120.152504

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