基于路径分析方法探究核耗散的形变关系

Investigating Deformation Dependence of Nuclear Dissipation Based on Pathwise Analysis Method

利用动力学加统计模型对200Pb系统的断前中子的发射进行了模拟。计算结果表明,在核耗散的形变关系(DDND)确定的情况下,断前中子多重性会随着能级密度坐标关系(DDLDP)的增强而减少,且该规律主要由第一阶段内断前中子的发射决定。此外,选定DDLDP而采用核耗散的不同形变关系也都很好地重现了实验数据。为了解释上述现象,提出了研究热核退激的路径分析方法,其主要内容是把核耗散看成是实验粒子在拉伸维度上的阻尼力,而核裂变的动力学过程是该阻尼力和自由能产生的驱动力之间相互竞争的结果。利用该方法对200Pb系统的断前中子多重性进行了分析,并指出在确定DDND时应考虑DDLDP。

Within a certain deformation dependence of nuclear dissipation （DDND）, the simulation results about the deexcitation process of 200Pb show that the prescission neutron multiplicities decrease with increasing deformation depen- dence of level density parameter （DDLDP）. Moreover, this pattern is determined by the emission of prescission neutron in the first period of nuclear fission. On the other hand, all of the results from two kinds of different DDNDs can reproduce the experiment data perfectly with a certain DDLDP. In order to illustrate those phenomena, the pathwise analysis method （PAM） is presented in this paper. In the PAM, nuclear dissipation is treated as the damping force on the elongation dimension, whereas the fission dynamics process results from the competition between damping force and the driving force stemming from the nuclear free energy. The prescission neutron multiplicity in the deexcitation process of 200pb is analyzed, and the results point out that the DDLDP needs to be taken into account in studying the DDND.