In-beam gamma-ray spectroscopy using fragmentation reactions of both stable and radioactive beams has been performed in order to study the structure of excited states in neutron-rich oxygen isotopes with masses ranging from A=20 to 24. For the produced fragments, gamma-ray energies, intensities, and gamma-gamma coincidences have been measured. Based on this information new level schemes are proposed for O-21,O-22 up to the neutron separation energy. The nonobservation of any gamma-decay branch from O-23 and O-24 suggests that their excited states lie above the neutron decay thresholds. From this, as well as from the level schemes proposed for O-21 and O-22, the size of the N=14 and 16 shell gaps in oxygen isotopes is discussed in the light of shell-model calculations.
N=14 and 16 shell gaps in neutron-rich oxygen isotopes / M. Stanoiu, F. Azaiez, Z. Dombradi, O. Sorlin, B. A. Brown, M. Belleguic, D. Sohler, M. G. Saint Laurent, M. J. Lopez Jimenez, Y. E. Penionzhkevich, G. Sletten, N. L. Achouri, J. C. Angelique, F. Becker, C. Borcea, C. Bourgeois, A. Bracco, J. M. Daugas, Z. Dlouhy, C. Donzaud, J. Duprat, Z. Fulop, D. Guillemaud Mueller, S. Grevy, F. Ibrahim, A. Kerek, A. Krasznahorkay, M. Lewitowicz, S. Lenhardt, S. Lukyanov, P. Mayet, S. Mandal, H. van der Marel, W. Mittig, J. Mrazek, F. Negoita, F. De Oliveira Santos, Z. Podolyak, F. Pougheon, M. G. Porquet, P. Roussel Chomaz, H. Savajols, Y. Sobolev, C. Stodel, J. Timar, A. Yamamoto. - In: PHYSICAL REVIEW. C, NUCLEAR PHYSICS. - ISSN 0556-2813. - 69:3(2004), pp. 034312.1-034312.10. [10.1103/PhysRevC.69.034312]
N=14 and 16 shell gaps in neutron-rich oxygen isotopes
A. Bracco;
2004
Abstract
In-beam gamma-ray spectroscopy using fragmentation reactions of both stable and radioactive beams has been performed in order to study the structure of excited states in neutron-rich oxygen isotopes with masses ranging from A=20 to 24. For the produced fragments, gamma-ray energies, intensities, and gamma-gamma coincidences have been measured. Based on this information new level schemes are proposed for O-21,O-22 up to the neutron separation energy. The nonobservation of any gamma-decay branch from O-23 and O-24 suggests that their excited states lie above the neutron decay thresholds. From this, as well as from the level schemes proposed for O-21 and O-22, the size of the N=14 and 16 shell gaps in oxygen isotopes is discussed in the light of shell-model calculations.
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