| 1. |
- Aksyutina, Yuliya, 1983, et al.
(författare)
-
Properties of the 7He ground state from 8He neutron knockout
- 2009
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693. ; 679:3, s. 191 - 196
-
Tidskriftsartikel (refereegranskat)abstract
- The unbound nucleus 7He, produced in neutron-knockout reactions with a 240 MeV/u 8He beam in a liquid-hydrogen target, has been studied in an experiment at the ALADIN-LAND setup at GSI. From an R-matrix analysis the resonance parameters for 7He as well as the spectroscopic factor for the 6He(0+) + n configuration in its ground-state have been obtained. The spectroscopic factor is 0.61 confirming that 7He is not a pure single-particle state. An analysis of 5He data from neutron-knockout reactions of 6He in a carbon target reveals the presence of an s-wave component at low energies in the α+n relative energy spectrum. A possible low-lying exited state in 7He observed in neutron knockout data from 8He in a carbon target and tentatively interpreted as a Iπ=1/2− state, could not be observed in the present experiment. Possible explanations of the shape difference between the 7He resonance obtained in the two knockout reactions are discussed in terms of target-dependence or different reaction mechanisms at relativistic energies.
|
|
| 2. |
- Alcorta, M., et al.
(författare)
-
Nuclear Structure of C-12 from Break-up Studies in Complete Kinematics
- 2009
-
Ingår i: AIP Conference Proceedings. - : AIP. - 1551-7616 .- 0094-243X. - 9780735407022 ; 1165, s. 27-30 461
-
Konferensbidrag (refereegranskat)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.
|
|
| 3. |
|
|
| 4. |
- Diget, C. A., et al.
(författare)
-
Breakup channels for C-12 triple-alpha continuum states
- 2009
-
Ingår i: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 80:3
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 5. |
- Hyldegaard, S., et al.
(författare)
-
Branching ratios in the beta decays of N-12 and B-12
- 2009
-
Ingår i: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 80:4
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 6. |
- Jeppesen, H. B., et al.
(författare)
-
Study of Li-10 via the Li-9(H-2, p) reaction at REX-ISOLDE
- 2006
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 642:5-6, s. 449-454
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 7. |
- Kirsebom, O. S., et al.
(författare)
-
Observation of gamma-delayed 3 alpha breakup of the 15.11 and 12.71 MeV states in C-12
- 2009
-
Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 680:1, s. 44-49
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 8. |
- Madurga, M., et al.
(författare)
-
beta-delayed particle studies of the halo nucleus Li-11 and its core Li-9
- 2008
-
Ingår i: AIP Conference Proceedings. - 1551-7616 .- 0094-243X. ; 1012, s. 193-197 453
-
Konferensbidrag (refereegranskat)abstract
- The beta-decay of Li-11 and its core Li-9 has been revisited with the aim to disentangle the very complex decays from unbound states in the daughters. The decay channels for the states fed by beta-decay in Be-9 are established including the 2.43 MeV state for which the analysis of alpha alpha and n alpha spectra seem to favour direct break-up of the level. For the decay of Li-11 the beta-delayed charged particle spectrum can be explained by the contribution of the 10.6 and 18.2 MeV states. The alpha alpha correlations indicates that decay through resonant He-isotopes are more likely than phase space distributed 5-body break-up.
|
|
| 9. |
- Madurga, M., et al.
(författare)
-
Evidence of a new state in Be-11 observed in the Li-11 beta-decay
- 2009
-
Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 677:5, s. 255-259
-
Tidskriftsartikel (refereegranskat)abstract
- Coincidences between charged particles emitted in the beta-decay of Li-11 were observed using highly segmented detectors. The breakup channels involving three particles were Studied in full kinematics allowing for the reconstruction of the excitation energy of the Be-11 states participating in the decay. In particular, the contribution of a previously unobserved state at 16.3 MeV in Be-11 has been identified selecting the alpha + He-7 -> alpha + He-6 + n channel. The angular correlations between the alpha particle and the center of mass of the He-6 + n system favors spin and parity assignment of 3/2(-) for this state as well as for the previously known state at 18 MeV. (C) 2009 Elsevier B.V. All rights reserved.
|
|
| 10. |
- Madurga, M., et al.
(författare)
-
Kinematic identification of the t branch in the decay of 11Li
- 2009
-
Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-601X .- 1434-6001. ; 42:3, s. 415-419
-
Tidskriftsartikel (refereegranskat)abstract
- The -delayed 8 Li + t branch of the 11Li decay was identified via kinematical analysis of the charged particles observed in coincidence. The back-to-back events observed in a narrow angular acceptance were compared to a Monte Carlo simulation. The 8 Li + t sum energy spectrum was fitted assuming that the decay occurs through an intermediate state in 11Be . The resulting energy centroid and full-width half maximum for the intermediate state are 18.35(30)MeV and 1.5(4)MeV, respectively. The -delayed 8 Li + t branching ratio obtained from the coincidence spectrum, BR t = 0.93(8)×10-4 , is in agreement with previous measurements but more precise.
|
|
