Structure des isotopes de bore et de carbone riches en neutrons aux limites de la stabilité

Abstract : The unbound nuclei 18B and 21C have been studied in an experiment undertaken at the RIBF-RIKEN using the recently commissioned SAMURAI spectrometer and NEBULA neutron array. The two systems were probed using single-neutron and single and two-proton knockout from secondary beams of 22C, 22N, et 23O respectively in the case of 21C and 19B, 19C and 20N for 18B. The invariant mass spectra were reconstructed from the momentum of the fragment (17B, 20C) and neutron. In order to interpret the results a complete simulation of the experimental setup was utilised. The analysis procedures as well as the calibrations were verified through a measurement of the well-known ground state of 16B. In the case of 18B three states were observed: an s-wave virtual state (as < -50 fm), an l=2 resonance at Er =0.77 +- 0.09 MeV and an l=0 resonance at Er = 1.6 +- 0.6 MeV. These results suggest that the low-lying level structure of 18B is governed by a competition between the neutron 2s1/2 and 1d5/2 configurations. In the case of 21C resonances were observed at Er = 0.8 +- 0.15 MeV (l = 0) and Er = 1.5 +-0.1 MeV (l=2), a result which confirms predictions of an inversion of the 5/2+ and 1/2+ levels. Finally an analysis of the momentum distributions for 18B and 21C produced in single-neutron knockout was carried out. The results indicate that the valence neutrons 19B and 22C are in mixed (2s1/2)2 and (1d5/2)2 configurations. 
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Contributor : Sylvain Leblond <>
Submitted on : Wednesday, March 16, 2016 - 4:00:10 PM
Last modification on : Tuesday, February 5, 2019 - 12:12:09 PM

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  • HAL Id : tel-01289381, version 1

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Sylvain Leblond. Structure des isotopes de bore et de carbone riches en neutrons aux limites de la stabilité. Physique Nucléaire Expérimentale [nucl-ex]. Normandie Université, France, 2015. Français. ⟨tel-01289381⟩

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