Suchergebnisse

5 pags., 2 figs. -- International Symposium on Nuclear Astrophysics - Nuclei in the Cosmos - IX 25-30 June 2006 CERN ; We have studied 12C in full kinematics via the 10B( 3He,pααα) reaction at 2.45 MeV. In our data we have identified states in 12C 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 12C resonances, such as their energy, width, and spin. In this contribution preliminary results from the ongoing analysis is presented. ; This work has been made possible by the CSIC I3P program, and is supported by the European Union under the Sixth framework project EURONS-contract number 506065. ; Peer reviewed

We have used the 10B(3He,p¿¿¿) reaction at 4.9 MeV and the 11B(3He,d¿¿¿) reaction at 8.5 MeV to determine the energy, width, and decay mechanism of resonances in 12C above the triple-¿ threshold up to 21 MeV in excitation energy. Comparison with various models has allowed us to estimate the degree of clustering of the states studied. © 2012 American Physical Society. ; Support by the Spanish Research Grant FPA2009-07387 and Consolider Project CSD2007-00042, by the European Union Sixth Framework through RII3- EURONS/ JRA4-DLEP (Contract No. 506065). Support of the CSIC I3P program cofinanced by the European Social Fund, and the support of the US Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357. O.S.K. Support from the Villum Kann Rasmussen Foundation. ; Peer Reviewed

6 pags., 4 figs., 2 tabs. -- PACS:27.20.+n25.55.Hp23.20.-g29.85.-c ; The 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.