| 1. |
- Alcorta, M., et al.
(author)
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Nuclear Structure of C-12 from Break-up Studies in Complete Kinematics
- 2009
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In: AIP Conference Proceedings. - : AIP. - 1551-7616 .- 0094-243X. - 9780735407022 ; 1165, s. 27-30 461
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Conference paper (peer-reviewed)abstract
- A complete kinematics study of the B-10(He-3,p alpha alpha alpha) and B-11(He-3,d alpha alpha alpha) reactions has been performed to study the multi-particle break-up of C-12 resonances above the triple-alpha threshold. Four-particle coincidence detection gives us complete information on the direction and energy of the individual alpha particles from the decay of C-12, allowing us to extract new information on the structure of C-12 which we shall present in this contribution. We have observed gamma de-excitation of the T=1 15.11 MeV resonance using charged particle detectors, and have constructed Dalitz plots of the individual resonances in C-12 using the complete kinematics information of the alpha particles which come from their break-up.
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| 2. |
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| 3. |
- Borge, M. J. G., et al.
(author)
-
Beta-delayed multiparticle emission studies at ISOL-type facilities
- 2004
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In: Nuclear Physics A. - : Elsevier BV. - 0375-9474. ; 746, s. 243-243
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Conference paper (peer-reviewed)abstract
- We report here on the recent beta-decay studies made at ISOL-type Facilities to determine the multiparticle breakup mechanism of excited states in light nuclei by studying them in full kinematics. In particular the results obtained for the A = 9 isobars and the breakup of the 12.7 MeV state in C-12 of unnatural parity are discussed. The breakup of the latter has been debated since more than a decade. Mirror beta transitions in the A = 9 chain are compared and a large asymmetry factor is deduced for the transitions to high excitation energy in Be-9 (11.8 MeV) and B-9 (12.2 MeV) fed in the beta-decay of Li-9 and C-9 respectively. It is shown that the asymmetry is not due to experimental problems or differences in the mechanisms of breakup or in the spin of the states. As no asymmetry is found in the gs to gs transition it must be due to the particular structure of these excited states. The controversy on the breakup mechanism of the 12.7 MeV state is resolved.
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| 4. |
- Borge, M. J. G., et al.
(author)
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Mapping of the C-12* states via the B-10(He-3,p alpha alpha alpha) reaction
- 2007
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In: European Physical Journal: Special Topics. - : Springer Science and Business Media LLC. - 1951-6401 .- 1951-6355. ; 150:1, s. 207-210
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Journal article (peer-reviewed)abstract
- We have studied C-12 in full kinematics via the B-10(He-3, p alpha alpha alpha) reaction at an energy of 2.45 MeV. In our data we have identified states in C-12 from the ground state up to about 18 MeV, with spins ranging from 0 to 4. Due to the very good resolution, we are able to determine properties of these C-12 resonances, such as their energy, width, and spin. In this contribution preliminary results from the ongoing analysis are presented. Main focus on the precise determination of the breakup spectra for all resonances.
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| 5. |
- Diget, C. A., et al.
(author)
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Breakup channels for C-12 triple-alpha continuum states
- 2009
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In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 80:3
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Journal article (peer-reviewed)abstract
- The triple-alpha-particle breakup of states in the triple-alpha continuum of C-12 has been investigated by way of coincident detection of all three alpha particles of the breakup. The states have been fed in the beta decay of N-12 and B-12, and the alpha particles measured using a setup that covers all of the triple-alpha phase space. Contributions from the breakup through the Be-8(0(+)) ground state as well as other channels-interpreted as breakup through excited energies in Be-8-have been identified. Spins and parities of C-12 triple-alpha continuum states are deduced from the measured phase-space distributions for breakup through Be-8 above the ground state by comparison to a fully symmetrized sequential R-matrix description of the breakup. At around 10 MeV in C-12, the breakup is found to be dominated by 0(+) strength breaking up through the ghost of the Be-8(0(+)) ground state with L = 0 angular momentum between the first emitted alpha particle and the intermediate Be-8 nucleus. For C-12 energies above the 12.7 MeV 1(+) state, however, L = 2 breakup of a C-12 2(+) state through the Be-8(2(+)) excited state dominates. Furthermore, the possibility of a 2(+) excited state in the 9-12 MeV region of C-12 is investigated.
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| 6. |
- Fynbo, H. O. U., et al.
(author)
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News on C-12 from beta-decay studies
- 2004
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In: Nuclear Physics A. - : Elsevier BV. - 0375-9474. ; 738, s. 59-65
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Conference paper (peer-reviewed)abstract
- We discuss the importance of the spectroscopic properties of the resonances of C-12 just above the 3alpha-threshold, and review the existing experimental information of this region with emphasis on 0(+) and 2(+) states. A new experimental approach for studying the beta-decays of B-12 and N-12 is presented based on techniques developed in the context of Radioactive beam (rare isotope) physics. Finally preliminary results from an ongoing analysis of two recent experiments are given.
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| 7. |
- Hyldegaard, S., et al.
(author)
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Branching ratios in the beta decays of N-12 and B-12
- 2009
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In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 80:4
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Journal article (peer-reviewed)abstract
- Absolute branching ratios to unbound states in C-12 populated in the beta decays of N-12 and B-12 are reported. Clean sources of N-12 and B-12 were obtained using the isotope separation on-line (ISOL) method. The relative branching ratios to the different populated states were extracted using single-alpha as well as complete kinematics triple-alpha spectra. These two largely independent methods give consistent results. Absolute normalization is achieved via the precisely known absolute branching ratio to the bound 4.44 MeV state in C-12. The extracted branching ratios to the unbound states are a factor of three more precise than previous measurements. Branching ratios in the decay of Na-20 are also extracted and used to check the results.
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| 8. |
- Hyldegaard, S., et al.
(author)
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R-matrix analysis of the beta decays of 12N and 12B
- 2010
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In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 81:2
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Journal article (peer-reviewed)abstract
- The β decays of 12N and 12B have been studied at KVI and JYFL to resolve the composition of the broad and interfering 0+ and 2+ strengths in the triple-α continuum. For the first time a complete treatment of 3α decay is presented including all major breakup channels. A multilevel, many-channel R-matrix formalism has been developed for the complete description of the breakup in combination with the recently published separate analysis of angular correlations. We find that, in addition to the Hoyle state at 7.65 MeV, more than one 0+ and 2+ state is needed to reproduce the spectra. Broad 03+ and 22+ states are found between 10.5 and 12 MeV in this work. The presence of β strength up to the 12N Q-value window suggests the presence of additional 0+ and 2+ components in the 12C structure at energies above 12.7 MeV.
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| 9. |
- Jeppesen, H. B., et al.
(author)
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Study of Li-10 via the Li-9(H-2, p) reaction at REX-ISOLDE
- 2006
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In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 642:5-6, s. 449-454
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Journal article (peer-reviewed)abstract
- The Click to view the MathML source reaction has been investigated at 2.36 MeV/u at the REX-ISOLDE facility. In this Letter we focus on the Click to view the MathML source channel which potentially holds spectroscopic information on the unbound nucleus 10Li. The experimental excitation energy spectrum and angular distribution are compared with CCBA calculations. These calculations clearly support the existence of a low-lying (s) virtual state, with a (negative) scattering length of the order asnot, vert, similar1324 fm and a p1/2 resonance with an energy of Ersimilar, equals0.38 MeV and a width of Γsimilar, equals0.2 MeV.
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| 10. |
- Kirsebom, O. S., et al.
(author)
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Observation of gamma-delayed 3 alpha breakup of the 15.11 and 12.71 MeV states in C-12
- 2009
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In: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 680:1, s. 44-49
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Journal article (peer-reviewed)abstract
- The reactions B-10(He-3, p alpha alpha alpha) at 4.9 MeV and B-11(He-3, d alpha alpha alpha) at 8.5 MeV have been used to investigate the gamma decay of states in C-12. By measuring the four-body final state in complete kinematics we are able to detect gamma transitions indirectly. We find gamma transitions from the 15.11 MeV state in C-12 to the 12.71, 11.83, 10.3 and 7.65 MeV states followed by their breakup into three alpha particles. The relative gamma-ray branching ratios obtained are (1.2 +/- 0.3), (0.32 +/- 0.12), (1.4 +/- 0.2) and (4.4 +/- 0.8)%, respectively, with the remaining (92.7 +/- 1.0)% of the gamma decays going to the bound states. We obtain Gamma(alpha)/Gamma = (2.8 +/- 1.2)% for the isospinforbidden alpha decay of the 15.11 MeV state. From the 12.71 MeV state we find gamma transitions to the 10.3 and 7.65 MeV states. The relative gamma-ray branching ratios are (0.9(-0.5)(+0.6)) and (2.6(-1.2)(+1.6))%, respectively, with the remaining (96.6(-1.3)(+1.7))% of the gamma decays going to the bound states. Finally. we discuss the relation between the beta decay of N-12 and B-12 to states in C-12 and the gamma decay of the 15.11 MeV analog in C-12 to the same states. (C) 2009 Elsevier B.V. All rights reserved.
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