| The nuclear friction is likely to stem from nuclear collisions with the nuclear surface,or nucleon-nucleon collisions in the nuclear surface region,which delays the large-scale collective deformation of a hot nuclei.Because the de-excitation of hot nuclei is essentially a thermodynamic process,hence the thermodynamic driving force(TDF)should be provided by nuclear free energy which derived from two aspects:one is the change of single-particle level structure;the other is the change of free energy caused by endothermic transition of nucleon in high excited state,which suggests that we should systematically study the influence of nuclear potential and nuclear level density parameter(LDP)on TDF.In order to study the effect of curvature energy on TDF,the potential and entropy barrier of 200Pb,210Po and 224Th systems are calculated by using the truncated droplet model including curvature energy.Compared with the liquid drop model,the results show that curvature energy does not affect the saddle point of 224Th,but pushes the saddle point of other two systems backwards the ground state.The stronger the deformation dependence of the level density parameter is,the closer the saddle point of entropy barrier for these systems is to the ground state.In order to further explore how curvature energy affects TDF through nuclear potential and entropy,respectively,the prescission neutron multiplicity(PNM)is selected as the probe,the simulations based on two schemes are carried out.The results show that curvature energy reduces the potential driving force of three systems,and enhances the entropy potential driving force.Combined with the calculations and analyses of PNM,the former effect is more obvious than the latter,so curvature energy weakens TDF of two systems on whole,thus delaying the nuclear fission process of three systems.In order to study the influence of shell correction on TDF,the effect of deformationdependent shell correction(DDSC)on the emission of prescission neutron(EPN)is studied within the framework of a one-dimensional Langevin model with self-contained deformation dependences for three isotopes of 213,215,217Fr near the neutron 126 closure-shell.The results show that the fission barriers are enhanced with DDSC,and the increment of 213Fr is higher than those of 215,217Fr,but those saddle points are not changed.Although the enhancement of fission barrier delays nuclear fission,the fission dynamics process is controlled by the competition between TDF and nuclear damping,so the deformation-dependence of nuclear dissipation must be considered in order to extract the role of shell correction.Taking the two stages of fission into account,the effect of DDSC on EPN near the neutron 126 closure-shell is dominated by the rules in the first phase of nuclear fission.In order to study the effect of deformation-dependent mass tensor(DDMT)and viscous tensor on the reduced thermodynamic driving force,we selected 200Pb,213Fr and 224Th and make the compared studies.The deformation dependence of nuclear friction does not change the positive position where the reduced TDF appears.With the increase of system mass,the reduced TDF calculated by SPS friction emerges a special phenomenon,namely,"fall of tide" tide" with the weakening of LDP deformation dependence,which is related to the barrier configuration of the system and the deformation dependence of LDP.After taking DDMT into account,the positive position of reduced TDF in the three systems generally moves backward,and its effect on reduced TDF mainly concentrates on the first stage of fission.Based on the requirement of model self-consistency,the Coulomb redistribution energy with deformation dependence(DDCRE)are taken into account for the calculations for potential and LDP,then we carry out a study about the effect of DDCRE on the emission of prescission particles.The results show that within the error range,Coulomb redistribution energy can hardly affect the prescission emission of charged particles. |
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