EPJ Web of Conferences (Jan 2016)

First simultaneous measurement of fission and gamma probabilities of 237U and 239Np via surrogate reactions

  • Marini P.,
  • Ducasse Q.,
  • Jurado B.,
  • Aiche M.,
  • Mathieu L.,
  • Barreau G.,
  • Czajkowski S.,
  • Tsekhanovich I.,
  • Moro A.,
  • Lei J.,
  • Giacoppo F.,
  • Gorgen A.,
  • Tornyi,
  • Audouin L.,
  • Tassan-Got L.,
  • Wilson J. N.,
  • Gunsing F.,
  • Guttormsen M.,
  • Larsen A. C.,
  • Lebois M.,
  • Renstrom T.,
  • Rose S.,
  • Siem S.,
  • Tveten G. M.,
  • Wiedeking M.,
  • Serot O.,
  • Boutoux G.,
  • Méot V.,
  • Morillon B.,
  • Denis-Petit D.,
  • Roig O.,
  • Oberstedt S.,
  • Oberstedt A.

DOI
https://doi.org/10.1051/epjconf/201612212004
Journal volume & issue
Vol. 122
p. 12004

Abstract

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Fission and gamma decay probabilities of 237U and 239Np have been measured, for the first time simultaneously in dedicated experiments, via the surrogate reactions 238U(3He, 4He) and 238U(3He,d), respectively. While a good agreement between our data and neutron-induced data is found for fission probabilities, gamma decay probabilities are several times higher than the corresponding neutron-induced data for each studied nucleus. We study the role of the different spin distributions populated in the surrogate and neutron-induced reactions. The compound nucleus spin distribution populated in the surrogate reaction is extracted from the measured gamma-decay probabilities, and used as input parameter in the statistical model to predict fission probabilities to be compared to our data. A strong disagreement between our data and the prediction is obtained. Preliminary results from an additional dedicated experiment confirm the observed discrepancies, indicating the need of a better understanding of the formation and decay processes of the compound nucleus.