Publications (6)0 Total impact
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María José García Borge,
U. C. Bergmann, Rafik Boutami,
J. Cederkäll,
P. Dendooven,
Luis M. Fraile,
H. O. U. Fynbo,
W. X. Huang,
J. Huikari,
Y. Jading, [......],
Ismael Martel,
M. Meister,
T Nilsson,
G. Nyman,
Yolanda Prezado,
K. Riisager,
Olof Tengblad,
L Weissman,
K. Wilhelmsen,
J. Äystö
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ABSTRACT: 5 pages, 1 table, 2 figures.-- Printed version published Dec 27, 2004.-- Issue title: Proceedings of the Sixth International Conference on Radioactive Nuclear Beams (RNB6, Argonne, Illinois, Sep 22-26, 2003). We report here on the recent β-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 β-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. Peer reviewed
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María José García Borge,
Yolanda Prezado,
U. C. Bergmann, Rafik Boutami,
J. Cederkäll,
C. Aa. Diget,
Luis M. Fraile,
H. O. U. Fynbo,
Y. Jading,
H. Jeppesen, [......],
Ismael Martel,
M. Meister,
T Nilsson,
G. Nyman,
K. Riisager,
H. Simon,
Olof Tengblad,
L Weissman,
F. Wenander,
K. Wilhelmsen
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ABSTRACT: 5 pages, 2 tables, 2 figures.-- Issue title: Proceedings of the 8th International Conference on Clustering Aspects of Nuclear Structure and Dynamics (Nara, Japan, Nov 24-29, 2003). We report here on the recent β-decay studies of the A = 9 isobar made at ISOLDE/CERN. 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 β-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. Only differences in the partial decay branches of the breakup channels have been found. As no asymmetry is found in the gs to gs transition it must be due to the particular structure of these excited states. Peer reviewed
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U. C. Bergmann,
María José García Borge, Rafik Boutami,
Luis M. Fraile,
H. O. U. Fynbo,
P Hornshøj,
B. Jonson,
K. Markenroth,
Ismael Martel,
I. Mukha,
T Nilsson,
G. Nyman,
A. Oberstedt,
Yolanda Prezado Alonso,
K. Riisager,
H. Simon,
Olof Tengblad,
F. Wenander,
K. Wilhelmsen Rolander
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ABSTRACT: 24 pages, 9 figures.-- PACS nrs.: 23.40.Hc; 27.20.+n; 24.80.+y.-- Available online 17 August 2001. In β-decay experiments on C-9 at CERN/ISOLDE the β-strength was determined to the ground state, the 12.2 MeV excited state and the Isobaric Analog State (IAS) at 14.655 MeV in B-9. A large β-strength asymmetry is deduced for the mirror transitions of C-9 and Li-9 to states around 12 MeV excitation energy. A satisfactory description of the three-body decay from a narrow energy region around the 12.2 MeV resonance is obtained within a sequential model involving the ground and first-excited states of Li-5 and Be-8. From the study of angular correlations the spin of the 12.2 MeV state is determined as 5/2(-). For the first time the population of the IAS is observed in β-decay and new information on the decay of this state is obtained. The advantages of a closely packed. highly segmented detector setup are demonstrated. This work was partly supported by BMBF, contract number 06DA915I and GSI contract number DARIK. The work was also partly supported by the Spanish CICYT “Plan Nacional de Altas Energías” under contract AEN-99-1046-C02-01. Peer reviewed
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H. Mach,
Luis M. Fraile,
Olof Tengblad, Rafik Boutami,
C. Jollet,
W. A. Plóciennik,
D. T. Yordanov,
M. Stanoiu,
María José García Borge,
P A Butler, [......],
W. Kurcewicz,
F. Marechal,
T. Motobayashi,
J. Mrazek,
G. Neyens,
T Nilsson,
S. Pedersen,
Alfredo Poves,
Berta Rubio,
E. Ruchowska
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ABSTRACT: 5 pages, 10 figures.-- PACS nrs.: 21.10.Tg; 23.20.Lv; 27.30.+t.-- Issue title: "ENAM 2004, Fourth International Conference on Exotic Nuclei and Atomic Masses" (Pine Mountain, Georgia, Sep 12-16, 2004). The fast timing βγγ(t) method was applied to investigate the level lifetimes in 30,31,32Mg. Levels in Mg have been populated in β and β-delayed neutron emission of Na, at the ISOLDE facility. From the γγ coincidences a number of new states have been identified and new level schemes were constructed for 30 31,32Mg. The following preliminary half lives have been determined: T-1/2 = 3.9(4) ns for the 1789 keV state in 30Mg, T-1/2 = 133(8) ps and 10.5(8) ns for the 221 keV and 461 keV states in 31Mg, respectively, and T-1/2 = 16(4) ps for the 885 keV level in 32Mg. The 1789 keV level was established as a candidate for the intruder 0(+) configuration in 30Mg with a possible strong E0 branch to the ground state. Peer reviewed
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H.H. Knudsen,
H. O. U. Fynbo,
María José García Borge, Rafik Boutami,
P. Dendooven,
C.Aa. Diget,
T. Eronen,
S. Fox,
Luis M. Fraile,
B. Fulton, [......],
I. Moore,
A. Nieminen,
G. Nyman,
H. Penttilä,
K. Riisager,
S. Rinta-Antila,
Olof Tengblad,
Y Wang,
K. Wilhelmsen,
J. Äystö
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ABSTRACT: 5 pages, 2 tables, 3 figures.--PACS nrs.: 23.40.Hc; 27.20.+n. The beta decay of O-13 has been studied at the IGISOL facility of the Jyvaskyla accelerator centre (Finland). By developing a low-energy isotope-separated beam of O-13 and using a modern segmented charged-particle detector array an improved measurement of the delayed proton spectrum was possible. Protons with energy up to more than 12 MeV are measured and the corresponding log(ft) values extracted. A revised decay scheme is constructed. The connection to molecular states and the shell model is discussed. This work was supported by the Academy of Finland under the Finnish Centre of Excellence Programme 2000–2005 (Project No. 44875, Nuclear and Condensed Matter Physics Programme at JYFL), by the European Union Fifth Framework Programme “Improving Human Potential - Access to Research Infrastructure” contract no. HPRI-CT-1999-00044, by the Spanish CICYT Agency under Project number FPA2002-04181-C04-02, and by the EU-RI3 (Integrated Infrastructure Initiative) under contract no 506065. Peer reviewed
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E. R. White,
H. Mach,
Luis M. Fraile,
U Köster,
O. Arndt,
A. Blazhev,
N. Boelaert,
María José García Borge, Rafik Boutami,
H. Bradley, [......],
J. Nyberg,
E. M. Reillo,
E. Ruchowska,
W. Schwerdtfeger,
G.S. Simpson,
M. Stanoiu,
Olof Tengblad,
P. G. Thirolf,
V. Ugryumov,
W. B. Walters
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ABSTRACT: 4 pages, 3 figures, 1 table.-- PACS nrs.: 21.10.Tg; 23.40.−s; 27.40.+z. The Advanced-Time-Delayed method was used to measure lifetimes of the states in Ar-41 populated in the β decay of Cl-41. The nuclei Cl-41 were produced at ISOLDE by 1.4-GeV proton bombardment of a thick UCx target and mass-separated as molecular ions, XeCl+. Our measured half-life of the 167.1-keV state, T(1/2) = 315(15) ps, is significantly lower than the previously measured value of 410(30) ps. We have also determined T(1/2) = 260(80) ps and T(1/2) ≤ 46 ps for the 515.9- and 1867.7-keV states, respectively. These are the shortest lifetimes measured so far with the ultrafast timing method using the new LaBr3(Ce) crystals for γ-ray detection. This work was performed as part of an undergraduate research project (ERW) at the Physics Department of the University of Notre Dame. Fast-timing detectors and electronics were provided by the Fast Timing Pool of Electronics. This study was supported in part by the NSF PHY04-57120, Swedish Research Council, BMBF Grant No. 06KY205I, the Alexander von Humboldt Foundation (WBW), Foundation for Polish Science (AK), the European Union Sixth Framework through RII3-EURONS (Contract No. 506065), and the EURTD project TARGISOL (HPRI-CT-2001-50033). Peer reviewed
