Effect of Friction on Neutron Emission in Fission of Heavy nuclei Jing-Dong Bao, Ying Jia Department of Physics, Beijing Normal University May 16-12, 2006 Shanghai, China

1. The parameterization 2. Stochastic calculation for angular distribution of fission fragment 3. Effect of friction on neutron emission 4. Summary

1.{c, h, α}parameterization of nuclear shape where c is the elongation, i.e., the distance of two centers of fragments ; h is the neck parameter; αis the asymmetrical parameter.

A set of Langevin equations test particles: .

Stochastic Runge-Kutta algorithm .

Time-dependent fission rate （ ） test particles passing over the saddle point first time test particles passing over the saddle point multi-times passing over the scission J. D. Bao, Y. Jia: PRC 69, 027602 (2004).

*During the Monte-Carlo simulating step, we compare time step and half decay period of neutron is a random number between 0 and 1，then emission of a neutron; * The nuclear inertial energy decreases with the emission of neutron。

Angular distribution of fission fragment Effective rotational moment defined at saddle-point and is always a random variable! is the temperature at the saddle point, calculated by Langevin simulation

3. One-body well plus window friction is window area The well formula is applied near the ground state; the window formula is addressed when the system arrives at the saddle point. In general, we have:

Neutron emission pre-scission for Th224

Other questions: The two-dimensional fission rate is (20-30%) larger than that of one dimension if the neck is considered; Dependence of Transport coefficients on temperature needs to consider in further work.

The saddle-point drifts into inside well and the fission barrier decreases with the emission of neutron

4. Summary The limitation of diffusion model：it is not suitable to quasi-fission problem, because an equilibrium shape is necessary. Underdamped motion before saddle-point and overdamped from saddle-point to scission point; (3) Temperature at saddle-point determined by the case of test particle leaving saddle point last time; (4)Oscillating time around saddle-point is the longest dynamical time scale, but it is influenced strongly by neutron emission.

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