No 1 FISSION DYNAMICS WITH MICROSCOPIC LEVEL DENSITIES ∗

Soon after the discovery of nuclear fission in 1938 [1], it was recognized that the process can be viewed qualitatively as an evolution of the nuclear shape from that of a single compound nucleus to two receding fragments [2,3] and that Langevin transport theory provides an appropriate model framework [3, 4]. A number of Langevin treatments of fission have been successfully developed and applied for excitations high enough to render the dynamics macroscopic, see, for example, Refs. [5–7]. If the collective shape dynamics is idealized as being highly dissipative, then the Langevin equation reduces to the Smoluchowski equation in which the evolution depends on the balance between the driving force provided by the potential energy of deformation and the dissipative force resulting from the coupling of the collective degrees of freedom to the remaining system. In this limit, it has proven possible to describe the Brownian shape motion as a Metropolis walk on the associated multi-dimensional deformation-energy