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Low-energy fission and beta-delayed fission with radioactive beams

Vendredi 4 mars 2016 11:00 - Duree : 1 heure
Lieu : Seminar Room 7/8 - ILL 1, 71 avenue des Martyrs, Grenoble

Orateur : A.N. ANDREYEV (Department of Physics, University of York, York, UK - Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Japan)

In the last decade, through technological, experimental and theoretical advances, the situation in experimental low-energy fission studies has changed dramatically. With the use of advanced production and detection techniques, much more detailed fission information can be obtained for traditional regions of fission research and, very importantly, new regions of nuclei have become accessible for fission studies.

The talk will give a review of recent low-energy fission experiments in very proton-rich nuclei in the lead region, with an emphasis on the exotic phenomenon of beta-delayed fission (bDF). This decay mode, which ideally suits to study low-energy fission, is experimentally accessible only in the well-studied uranium region and in the scarcely-studied (by fission) neutron-deficient lead region. Our pioneering bDF study of 180Tl at ISOLDE(CERN) showed an unexpected asymmetric fission-fragment mass split for 180Hg [1], despite a symmetric split in two semi-magic 90Zr nuclei was expected. This result also identified a new region of asymmetric fission in addition to the well-known asymmetry in trans-uranium nuclei.

More recently, new bDF data on the neutron-deficient nuclides 194,196At and 200,202Fr were obtained at ISOLDE. A mixture of asymmetric and symmetric fission is clearly seen in respective daughter isotopes (after precursor’s beta decay) 194,196Po and 202Rn [2]. This establishes a phenomenon of multimodal fission in this region of nuclei. The results will be compared with predictions from several current fission models.

As a conclusion, further perspective of low-energy fission studies with radioactive beams will be presented.

1. A. N. Andreyev et al., “New type of asymmetric fission in proton-rich nuclei”, Phys. Rev. Lett. 105, 252502 (2010)

2. L. Ghys et al., “Evolution of fission-fragment mass distributions in the neutron-deficient lead region”, Phys. Rev. C90, 041301(R) (2014)

*On behalf of the IS466/IS534 collaboration : RILIS-ISOLDE(CERN) – University of York (UK) – IKS, KU Leuven (Belgium) – Comenius University, Bratislava (Slovakia), JAEA, Tokai (Japan) – SCK•CEN, Mol (Belgium)

Contact : tellier@ill.fr

Discipline évènement : (Physique)
Entité organisatrice : (ILL)
Nature évènement : (Séminaire)
Evènement répétitif : (General ILL Seminar - College 3)
Site de l'évènement : Polygone scientifique

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