Fission process of low excited nuclei with Langevin approach

Abstract

Fragment mass distributions from the fission of U and Pu isotopes at low excitation energies are studied using a dynamical model based on the fluctuation-dissipation theorem formulated as Langevin equations. The present calculations reproduced the overall trend of the asymmetric mass distribution without parameter adjustment for the first time using the Langevin approach. The Langevin trajectories show a complicated time evolution on the potential surface, which causes the time delay of fission, showing that dynamical treatment is vital. It was found that the shell effect of the potential energy landscape has a dominant role in determining the mass distribution, although it is rather insensitive to the strength of dissipation. Nevertheless, it is essential to include the effect of dissipation, since it has a crucial role in giving "fluctuation" to Langevin trajectories as well as for explaining the multiplicities of pre-scission neutrons as the excitation energy increases. Therefore, the present approach can serve as a basis for more refined analysis.

7 pages, 11 figures

References in corpus (3)

• Brownian shape motion on five-dimensional potential-energy surfaces: Nuclear fission-fragment mass distributions
• Prescission neutron multiplicity and fission probability from Langevin dynamics of nuclear fission
• Non-Markovian large amplitude motion and nuclear fission

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• Benchmark of the GEF model for fission-fragment yields over an enlarged range
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• Postfission properties of uranium isotopes: A hybrid method with Langevin dynamics and the Hauser-Feshbach statistical model
• A microscopic calculation of fission cross sections with the non-equilibrium Green function method
• Signature of bi-modal fission in Uranium nuclei
• Semi-empirical model to determine pre- and post-neutron fission product yields and neutron multiplicity