1. 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

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

3. 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.

5. A set of Langevin equations
test particles: .

6. Stochastic Runge-Kutta algorithm.

7. 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, (2004).

8. *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。

10. 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

12. 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:

14. Neutron emission pre-scission for Th224

15. 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.

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

17. 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.

18. Thanks !