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arXiv · 1812.08880

First observation of unbound $^{11}$O, the mirror of the halo nucleus $^{11}$Li

T. B. Webb·S. M. Wang·K. W. Brown·R. J. Charity·J. M. Elson·J. Barney·G. Cerizza·Z. Chajecki·J. Estee·D. E. M. Hoff·S. A. Kuvin·W. G. Lynch·J. Manfredi·D. McNeel·P. Morfouace·W. Nazarewicz·C. D. Pruitt·C. Santamaria·J. Smith·L. G. Sobotka·S. Sweany·C. Y. Tsang·M. B. Tsang·A. H. Wuosmaa·Y. Zhang·Z. Zhu
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Abstract

The structure of the extremely proton-rich nucleus $^{11}_{~8}$O$_3$, the mirror of the two-neutron halo nucleus $^{11}_{~3}$Li$_8$, has been studied experimentally for the first time. Following two-neutron knockout reactions with a $^{13}$O beam, the $^{11}$O decay products were detected after two-proton emission and used to construct an invariant-mass spectrum. A broad peak of width $\sim$3\,MeV was observed. Within the Gamow coupled-channel approach, it was concluded that this peak is a multiplet with contributions from the four-lowest $^{11}$O resonant states: $J^{\pi}$=3/2$^-_1$, 3/2$^-_2$, 5/2$^+_1$, and 5/2$^+_2$. The widths and configurations of these states show strong, non-monotonic dependencies on the depth of the $p$-$^9$C potential. This unusual behavior is due to the presence of a broad threshold resonant state in $^{10}$N, which is an analog of the virtual state in $^{10}$Li in the presence of the Coulomb potential. After optimizing the model to the data, only a moderate isospin asymmetry between ground states of $^{11}$O and $^{11}$Li was found.

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T. B. Webb, S. M. Wang, K. W. Brown, R. J. Charity, J. M. Elson, J. Barney, G. Cerizza, Z. Chajecki, J. Estee, D. E. M. Hoff, S. A. Kuvin, W. G. Lynch, J. Manfredi, D. McNeel, P. Morfouace, W. Nazarewicz, C. D. Pruitt, C. Santamaria, J. Smith, L. G. Sobotka, S. Sweany, C. Y. Tsang, M. B. Tsang, A. H. Wuosmaa, Y. Zhang, Z. Zhu. 2018-12-20. First observation of unbound $^{11}$O, the mirror of the halo nucleus $^{11}$Li. https://doi.org/10.1103/physrevlett.122.122501

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