| 1. |
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| 2. |
- Cubero, M., et al.
(author)
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Do Halo Nuclei Follow Rutherford Elastic Scattering at Energies Below the Barrier? The Case of 11Li
- 2012
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In: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 109:26
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Journal article (peer-reviewed)abstract
- The first measurement of the elastic scattering of the halo nucleus 11Li and its core 9Li on 208Pb at energies near the Coulomb barrier is presented. The 11Li+208Pb elastic scattering shows a strong reduction with respect to the Rutherford cross section, even at energies well below the barrier and down to very small scattering angles. This drastic change of the elastic differential cross section observed in 11Li+208Pb is the consequence of the halo structure of 11Li, as it is not observed in the elastic scattering of its core 9Li at the same energies. Four-body continuum-discretized coupled-channels calculations, based on a three-body model of the 11Li projectile, are found to explain the measured angular distributions and confirm that the observed reduction is mainly due to the strong Coulomb coupling to the dipole states in the low-lying continuum of 11Li. These calculations suggest the presence of a low-lying dipole resonance in 11Li close to the breakup threshold.
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| 3. |
- Cubero, M., et al.
(author)
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Elastic scattering of 9Li on 208Pb at energies around the Coulomb barrier
- 2011
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In: AIP Conference Proceedings. - : AIP. - 1551-7616 .- 0094-243X. - 9780735409378 ; 1377, s. 338-340
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Conference paper (peer-reviewed)abstract
- We have studied the dynamical effects of the halo structure of 11Li on the scattering on heavy targets at energies around the Coulomb barrier. This experiment was performed at ISAC‐II at TRIUMF with a world record in production of the post‐accelerated 11Li beam. As part of this study we report here on the first measurement of the elastic cross section of the core nucleus, i.e. 9Li on 208Pb, at energies around the Coulomb barrier. A preliminary optical model analysis has been performed in order to extract a global optical potential to describe the measured angular distributions.
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| 4. |
- Fernandez-Garcia, J. P., et al.
(author)
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11Li Breakup on 208Pb at Energies Around the Coulomb Barrier
- 2013
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In: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 110:14
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Journal article (peer-reviewed)abstract
- The inclusive breakup for the Li-11 + Pb-208 reaction at energies around the Coulomb barrier has been measured for the first time. A sizable yield of Li-9 following the Li-11 dissociation has been observed, even at energies well below the Coulomb barrier. Using the first-order semiclassical perturbation theory of Coulomb excitation it is shown that the breakup probability data measured at small angles can be used to extract effective breakup energy as well as the slope of B(E1) distribution close to the threshold. Four-body continuum-discretized coupled-channels calculations, including both nuclear and Coulomb couplings between the target and projectile to all orders, reproduce the measured inclusive breakup cross sections and support the presence of a dipole resonance in the Li-11 continuum at low excitation energy.
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| 5. |
- 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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| 6. |
- Kirsebom, O. S., et al.
(author)
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Breakup of 12C resonances into three α particles
- 2010
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In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 81:6
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Journal article (peer-reviewed)abstract
- The reaction He-3 + B-11 -> d + C-12* has been used to populate resonances in C-12 up to an excitation energy of 15 MeV. The subsequent breakup to three alpha particles has been measured in complete kinematics. Dalitz plots are used to visualize and analyze the data. The Dalitz plot intensity distribution exhibits zero points characteristic of the total spin and parity of the 3 alpha system allowing us to determine the spin and parity of a state in C-12 at 13.35 MeV whose quantum numbers were hitherto not well established. The Dalitz plot intensity distributions of the 2(-) state at 11.83 MeV and the 1(+) state at 12.71 MeV are compared with the predictions of a recent three-body calculation as well as with simpler models. All are able to reproduce the gross structures seen in the Dalitz plot, but none give an accurate description of the detailed profile of the distributions.
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| 7. |
- Kirsebom, O. S., et al.
(author)
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Improved Limit on Direct α Decay of the Hoyle State
- 2012
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In: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 108:20, s. 202501-
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Journal article (peer-reviewed)abstract
- The current evaluation of the triple-α reaction rate assumes that the α decay of the 7.65 MeV, 0+ state in 12C, commonly known as the Hoyle state, proceeds sequentially via the ground state of 8Be. This assumption is challenged by the recent identification of two direct α-decay branches with a combined branching ratio of 17(5)%. If correct, this would imply a corresponding reduction in the triple-α reaction rate with important astrophysical consequences. We have used the 11B(3He,d) reaction to populate the Hoyle state and measured the decay to three α particles in complete kinematics. We find no evidence for direct α-decay branches, and hence our data do not support a revision of the triple-α reaction rate. We obtain an upper limit of 5×10-3 on the direct α decay of the Hoyle state at 95% C.L., which is 1 order of magnitude better than a previous upper limit.
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| 8. |
- Kirsebom, O. S., et al.
(author)
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Precise and accurate determination of the B-8 decay spectrum
- 2011
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In: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 83:6
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Journal article (peer-reviewed)abstract
- Accurate measurements of the B-8 neutrino spectrum are important for the interpretation of solar neutrino data. Experimentally, the B-8 neutrino spectrum can be obtained from the measurement of the beta-delayed alpha spectrum. We report on an alpha-alpha coincidence measurement performed at the IGISOL facility in Jyvaskyla, Finland. Our measurement allows extensive cross-checks to be performed and gives a more intense neutrino spectrum at high energies compared to the present standard. The deviation reaches 4% at the end point of the spectrum. Below 11 MeV, the deviation is less than 1%.
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