Fission mechanism inferred from nuclear shape fluctuation by the Langevin equation

ランジュバン方程式による原子核形状揺動で考察した核分裂

有友 嘉浩*; 岩本 昭*; 西尾 勝久   ; 太田 雅久*

Aritomo, Yoshihiro*; Iwamoto, Akira*; Nishio, Katsuhisa; Ota, Masahisa*

One of the dynamical investigations for an understanding of the fission process is the analysis through Langevin trajectories in the nuclear deformation space. The main motivation of this analysis is to elucidate the characteristic nuclear-shape oscillation induced by a random force in the Langevin equation and its impact on the fission process. The characteristic random oscillation originates from the requirement of an overdamped condition. The properties of the friction tensor in the equation reveal that the directional nuclear shape fluctuations originate in the subspace of nuclear deformation. Our calculations exhibit a good agreement with the fission data for fermium isotopes, where the fission-fragment mass distribution changes dramatically from the asymmetric shape to the sharp symmetric shape as the masses of the fissioning Fm isotopes increase.