中子蒸發與裂變碎片關聯性研究

1、Effect of Friction on Neutron Emission in Fission of Heavy nuclei,May 16-12, 2006 Shanghai, China,Jing-Dong Bao, Ying JiaDepartment of Physics, Beijing Normal University,,1. The parameterization 2. Stochastic cal

2、culation 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

3、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 r

4、ate （　?。?,test particles passing over the saddle point first time,test particles passing over the saddle point multi-times,,J. D. Bao, Y. Jia: PRC 69, 027602 (2004).,,passing over the scission,,*During the Monte-Carlo si

5、mulating 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。,,,

6、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 p

7、lus 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-

8、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 furth

9、er 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 equi

10、librium 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 poin