Structure of $^{13}$Be probed via secondary beam reactions
| Autor: | Randisi, G., Leprince, A., Falou, H. Al, Orr, N. A., Marqués, F. M., Achouri, N. L., Angélique, J. -C., Ashwood, N., Bastin, B., Bloxham, T., Brown, B. A., Catford, W. N., Curtis, N., Delaunay, F., Freer, M., Brennand, E. de Góes, Haigh, P., Hanappe, F., Harlin, C., Laurent, B., Lecouey, J. -L., Ninane, A., Patterson, N., Price, D., Stuttgé, L., Thomas, J. S. |
|---|---|
| Rok vydání: | 2013 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1103/PhysRevC.89.034320 |
| Popis: | The low-lying level structure of the unbound neutron-rich nucleus $^{13}$Be has been investigated via breakup on a carbon target of secondary beams of $^{14,15}$B at 35 MeV/nucleon. The coincident detection of the beam velocity $^{12}$Be fragments and neutrons permitted the invariant mass of the $^{12}$Be+$n$ and $^{12}$Be+$n$+$n$ systems to be reconstructed. In the case of the breakup of $^{15}$B, a very narrow structure at threshold was observed in the $^{12}$Be+$n$ channel. Contrary to earlier stable beam fragmentation studies which identified this as a strongly interacting $s$-wave virtual state in $^{13}$Be, analysis here of the $^{12}$Be+$n$+$n$ events demonstrated that this was an artifact resulting from the sequential-decay of the $^{14}$Be(2$^+$) state. Single-proton removal from $^{14}$B was found to populate a broad low-lying structure some 0.70 MeV above the neutron-decay threshold in addition to a less prominent feature at around 2.4 MeV. Based on the selectivity of the reaction and a comparison with (0-3)$\hbar\omega$ shell-model calculations, the low-lying structure is concluded to most probably arise from closely spaced J$^\pi$=1/2$^+$ and 5/2$^+$ resonances (E$_r$=0.40$\pm$0.03 and 0.85$^{+0.15}_{-0.11}$ MeV), whilst the broad higher-lying feature is a second 5/2$^+$ level (E$_r$=2.35$\pm$0.14 MeV). Taken in conjunction with earlier studies, it would appear that the lowest 1/2$^+$ and 1/2$^-$ levels lie relatively close together below 1 MeV. Comment: 14 pages, 13 figures, 2 tables. Accepted for publication in Physical Review C |
| Databáze: | arXiv |
| Externí odkaz: |
|