Observation of γ-delayed 3α breakup of the 15.11 and 12.71 MeV states in 12C

6 pags., 4 figs., 2 tabs. -- PACS:27.20.+n25.55.Hp23.20.-g29.85.-cThe reactions 10B (3He, p α α α) at 4.9 MeV and 11B (3He, d α α α) at 8.5 MeV have been used to investigate the γ decay of states in 12C. By measuring the four-body final state in complete kinematics we are able to detect γ transitions indirectly. We find γ transitions from the 15.11 MeV state in 12C to the 12.71, 11.83, 10.3 and 7.65 MeV states followed by their breakup into three α particles. The relative γ-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 γ decays going to the bound states. We obtain Γα / Γ = (2.8 ± 1.2) % for the isospin-forbidden α decay of the 15.11 MeV state. From the 12.71 MeV state we find γ transitions to the 10.3 and 7.65 MeV states. The relative γ-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 γ decays going to the bound states. Finally, we discuss the relation between the β decay of 12N and 12B to states in 12C and the γ decay of the 15.11 MeV analog in 12C to the same states. © 2009 Elsevier B.V.We would like to acknowledge the support of the Spanish CICYT research grant FPA2007-62170 and the MICINN Consolider Project CSD 2007-00042 as well as the support of the European Union VI Framework through RII3-EURONS/JRA4-DLEP (contract number 506065). D.G. is a Juan de la Cierva fellow

Sub-barrier fusion cross section measurements with STELLA

The experimental setup STELLA (STELlar LAboratory) is designed for the measurement of deep sub-barrier light heavy ion fusion cross sections. For background suppression the γ-particle coincidence technique is used. In this project, LaBr3 detectors from the UK FATIMA (FAst TIMing Array) collaboration are combined with annular silicon strip detectors customized at IPHC-CNRS, Strasbourg, and the setup is located at Andromède, IPN, Orsay. The commissioning of the experimental approach as well as a sub-barrier 12C +12C → 24Mg∗ cross section measurement campaign are carried out

The 8B Neutrino Spectrum

6 pags., 2 figs. -- 11th Symposium on Nuclei in the Cosmos, NIC XI, July 19-23, 2010, Heidelberg, GermanyKnowledge of the energy spectrum of the neutrinos emitted in the β decay of 8B in the Sun is needed to interpret the neutrino spectrum measured on Earth. Experimentally, the 8B neutrino spectrum may be extracted from the measurement of the β-delayed α spectrum. In this contribution, the results of a recent α-α coincidence measurement are presented and compared to previous measurements. The implications for the neutrino spectrum are clarified.Peer reviewe

Scattering of halo nuclei on heavy targets at energies around the Coulomb barrier : The case of 11Be on 197Au

This work reports on the scattering of 11Be on 197Au at energies around and below the Coulomb barrier. By experimentally identifying the elastic scattering, inelastic scattering and breakup channels, and comparing them with different calculations, valuable information on the 11Be structure and its B(E1) distribution to the continuum are obtained. On top of that, a deeper understanding of the scattering process at low energies is achieved for reactions of this kind, making these studies extendable to other loosely-bound systems like 17,19

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Original Article: S. J. Freedman, K. E. Rehm, J. P. Schiffer, and D. Seweryniak, Comment on "Precise Determination of the Unperturbed 8B Neutrino Spectrum", Phys. Rev. Lett. 109, 189201 (2012)

Precise and accurate determination of the B8 decay spectrum

Accurate measurements of the B8 neutrino spectrum are important for the interpretation of solar neutrino data. Experimentally, the B8 neutrino spectrum can be obtained from the measurement of the β-delayed α spectrum. We report on an α-α coincidence measurement performed at the IGISOL facility in Jyväskylä, 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%. © 2011 American Physical Society.This work has been supported by the EU 6th Framework Programme “Integrating Infrastructure Initiative— Transnational Access,” Contract No. 506065 (EURONS, JRAs TRAPSPEC and DLEP), by the Academy of Finland under the Finnish Centre of Excellence Programme 2006-2011 (Project No. 213503, Nuclear and Accelerator Based Physics Programme at JYFL), by the Nordic Infrastructure Project (NordForsk Project No. 070315), and by the Spanish Funding Agency MICINN (Contract No. FPA2009-07387).Peer Reviewe

Observation of α decay from a state in 10B at 11.48 MeV

We report on the observation of α decay from a state in 10B at 11.48 MeV. The only observed decay branch is to the first T=1 state in 6Li at 3.56 MeV. The apparent absence of an α-decay branch to the (T=0) ground state in 6Li suggests that the 11.48-MeV state should be assigned isospin T=1. The spin and parity of the 11.48-MeV state could not be directly determined from the present study apart from J=0 being ruled out by the observed angular correlation. We conjecture that the 11.48-MeV state is the analog of the 10.15-MeV, (4 +) state in 10Be, constitutes the third member of a rotational band built on the 0 + state at 7.65 MeV, and has pronounced molecular structure. © 2012 American Physical Society.Support of the Spanish CICYT research Grant No. FPA2009-07387 and the MICINN Consolider Project No. CSD 2007-00042 as well as the support of the European Union VI Framework through RII3-EURONS/JRA4-DLEP (Contract No. 506065). OSK acknowledges support from the Villum Kann Rasmussen Foundation.Peer Reviewe

Analysis of the response of silicon detectors to α particles and 16^{16}O ions

We clarify basic concepts concerning the response of silicon detectors to ionizing radiation, focusing on light ions with energies ranging from a few hundred keV to a few MeV. Through reanalysis of existing experimental data, we quantify the difference in the response of silicon detectors to α particles and 16O ions, and we determine the correction that must be made before an energy calibration obtained with α particles can be applied to the measurement of 16O ions. Finally, we show that an apparent disagreement among three recent measurements of the decay spectrum of 8B can be explained by a failure to correctly take into account the different response of silicon detectors to α particles and 16O ions

Erratum: Precise and accurate determination of the 8B decay spectrum (Physical Review C (2011) 83 (065802)

Peer Reviewe

New β-delayed proton lines from 23 Al

We report on a new measurement of the β-delayed proton spectrum of 23Al. Higher statistics compared to previous measurements allow us to identify new proton lines in the energy range 1–2 MeV. A statistical analysis of the observed β strength shows that the B (GT) values are fully consistent with having a Porter-Thomas distribution. This is indicative of chaotic behaviour and implies that only the average β strength carries physical meaning.This work has been supported by the EU 6th Framework Programme “Integrating Infrastructure Initiative—Transnational Access”, Contract No. 506065 (EURONS, JRAs TRAPSPEC and DLEP), by the Academy of Finland under the Finnish Centre of Excellence Programme 2006-2011 (Project No. 213503, Nuclear and Accelerator Based Physics Programme at JYFL), by the Nordic Infrastructure Project (NordForsk Project No. 070315) and by the Spanish Funding Agency MICINN (Contract No. FPA2009-07387).Peer Reviewe