title: Fission barrier of superheavy nuclei and persistence of shell effects at high spin: cases of 254No and 220Th.
abstract: We report on the first measurement of the fission barrier height in a heavy shell-stabilized nucleus. The fission barrier height of 254No is measured to be Bf=6.0±0.5  MeV at spin 15ℏ and, by extrapolation, Bf=6.6±0.9  MeV at spin 0ℏ. This information is deduced from the measured distribution of entry points in the excitation energy versus spin plane. The same measurement is performed for 220Th and only a lower limit of the fission barrier height can be determined: Bf(I)>8  MeV. Comparisons with theoretical fission barriers test theories that predict properties of superheavy elements.
authors.affiliation: CSNSM, IN2P3-CNRS, and Université Paris Sud, Bat. 104-108, F-91405 Orsay, France and Argonne National Laboratory, Argonne, Illinois 60439, USA.
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authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.
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authors.initials: TL
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authors.affiliation: CSNSM, IN2P3-CNRS, and Université Paris Sud, Bat. 104-108, F-91405 Orsay, France.
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authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.
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authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.
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authors.affiliation: Advanced Science Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195, Japan.
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authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.
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authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.
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authors.affiliation: GANIL, CEA-DSM, and IN2P3-CNRS, B.P. 55027, F-14076 Caen Cedex, France and Université de Caen Basse-Normandie, F-14032 Caen Cedex, France.
authors.forename: D
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authors.lastname: Boilley
authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.
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authors.lastname: Carpenter
authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA and University of Maryland, College Park, Maryland 20742, USA.
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authors.initials: CJ
authors.lastname: Chiara
authors.affiliation: University of Massachusetts Lowell, Lowell, Massachusetts 01854, USA.
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authors.lastname: Chowdhury
authors.affiliation: Université de Strasbourg, IPHC, 23 rue du Loess, 67037 Strasbourg, France and CNRS, UMR7178, 67037 Strasbourg, France.
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authors.lastname: Gall
authors.affiliation: Department of Physics, University of Jyväskylä, FI-40014 Jyväskylä, Finland.
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authors.initials: PT
authors.lastname: Greenlees
authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA and DePaul University, Chicago, Illinois 60604, USA.
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authors.lastname: Gürdal
authors.affiliation: CSNSM, IN2P3-CNRS, and Université Paris Sud, Bat. 104-108, F-91405 Orsay, France.
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authors.initials: K
authors.lastname: Hauschild
authors.affiliation: Fundamental Fysik, Chalmers Tekniska Hogskola, 412 96 Göteborg, Sweden and WNSL, Yale University, New Haven, Connecticut 06511, USA.
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authors.lastname: Heinz
authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.
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authors.initials: CR
authors.lastname: Hoffman
authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: R V F
authors.initials: RV
authors.lastname: Janssens
authors.affiliation: Flerov Laboratory of Nuclear Reactions, JINR, Dubna, 141980, Russia.
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authors.initials: AV
authors.lastname: Karpov
authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.
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authors.lastname: Kay
authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.
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authors.initials: FG
authors.lastname: Kondev
authors.affiliation: University of Massachusetts Lowell, Lowell, Massachusetts 01854, USA.
authors.forename: S
authors.initials: S
authors.lastname: Lakshmi
authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.
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authors.lastname: Lauritsen
authors.affiliation: University of Massachusetts Lowell, Lowell, Massachusetts 01854, USA.
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authors.lastname: Lister
authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.
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authors.lastname: McCutchan
authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.
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authors.lastname: Nair
authors.affiliation: Université de Strasbourg, IPHC, 23 rue du Loess, 67037 Strasbourg, France and CNRS, UMR7178, 67037 Strasbourg, France.
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authors.lastname: Piot
authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.
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authors.affiliation: Institut für Kernphysik, Universität zu Köln, D-50937 Köln, Germany.
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authors.lastname: Reiter
authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.
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authors.affiliation: IPN, CNRS/IN2P3, Université Paris-Sud 11, F-91406 Orsay Cedex, France.
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authors.lastname: Rowley
authors.affiliation: Argonne National Laboratory, Argonne, Illinois 60439, USA.
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