Nuclear fission viewed as a diffusion process: Case of very large friction

Using a Fokker-Planck equation, we consider induced nuclear fission for large values of the friction constant. Then, the equation simplifies to the Smoluchowski equation which we solve using a method of van Kampen. We find that the fission rate obeys a scaling law. From our numerical results and those obtained previously, we estimate the transient time $\tau$ for fission. For small nuclear temperature, $\tau$ is defined as the time delay between the onset of a nuclear reaction and the attainment of the quasistationary probability flow over the fission barrier. For nuclear temperatures large compared to the fission barrier, the entire fission process is governed by transients, and $\tau$ essentially yields the fission lifetime. We speculate on the significance of our results for recent experimental observations.