1305.6132 (Y. Aritomo et al.)

Fission process of low excited nuclei with Langevin approach    [PDF]

Y. Aritomo, S. Chiba

Fragment mass distributions from fission of U and Pu isotopes at low excitation energies are studied with 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 in terms of the Langevin approach. The Langevin trajectories show complicated time evolution on the potential surface which causes time delay of fission, showing that dynamical treatment is vital. It was found that the shell effects of the potential-energy landscape has the dominant role to determine the mass distribution, while it is rather insensitive to the strength of dissipation. Still, it is indispensable to include the effect of dissipation since it gives a crucial role to give "fluctuation" to Langevin trajectories as well as to explain multiplicities of pre-scission neutrons as excitation energy increases. Therefore, the present approach can serve as a basis for more refined analysis.

View original: http://arxiv.org/abs/1305.6132