Effects of Deformation-dependent Shell Correction on Isotope Effect of Emission of Prescission Neutron near Neutron 126 Closure-shell
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摘要: 利用动力学加统计模型就形变相关的壳修正（DDSC）对中子126壳层附近209，213，217Fr断前中子发射的影响进行了研究。模拟结果表明，DDSC抬升了复合核的裂变位垒，且213Fr的升高约为209，217Fr的2倍，但却没有改变鞍点位置。尽管位垒升高延缓了系统的裂变，但其动力学过程受热力学驱动力（TDF）和核阻尼间竞争的主导，因此准确提取壳修正的作用还需考虑核耗散的形变关系。在裂变第一阶段，当核耗散取一体耗散（OBD）参数时，壳修正没有改变断前中子发射的同位素效应，然而当核耗散取标准参数设置（SPS）时，由于213Fr的TDF存在着异常增强，故该规律未能展现。在裂变第二阶段，位垒升高引起的断前中子发射的增强受到了TDF与核阻尼间竞争的反制，故断前中子发射的同位素效应仍未能显现。综合两阶段情况，DDSC对N=126处断前中子发射的同位素效应的影响受第一阶段规律的支配。
The effect of deformation-dependent shell correction (DDSC) on the emission of prescission neutron (EPN) is studied within a dynamical and statistical model for three isotopes of 209,213,217Fr near the neutron 126 closure-shell. The results show that the fission barriers are enhanced with DDSC, and the increment of 213Fr is almost 2 times those of 209,217Fr, 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 thermodynamic driving force (TDF) and nuclear damping, so the deformation-dependence of nuclear dissipation must be considered in order to extract the role of shell correction. The shell correction doesn't alter isotope effect of EPN with OBD nuclear dissipation in the first phase of nuclear fission, but the rule does not been exhibited because that there is abnormal enhancement of TDF using SPS nuclear dissipation. The increment of EPN caused by the rise of fission barrier is countered by the competition between TDF and nuclear damping in the second phase of nuclear fission, hence the effect of EPN cannot exhibit. The effect of DDSC on EPN near the neutron 126 closure-shell is dominated by the rules in the first phase of nuclear fission.Abstract: The effect of deformation-dependent shell correction (DDSC) on the emission of prescission neutron (EPN) is studied within a dynamical and statistical model for three isotopes of 209,213,217Fr near the neutron 126 closure-shell. The results show that the fission barriers are enhanced with DDSC, and the increment of 213Fr is almost 2 times those of 209,217Fr, 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 thermodynamic driving force (TDF) and nuclear damping, so the deformation-dependence of nuclear dissipation must be considered in order to extract the role of shell correction. The shell correction doesn't alter isotope effect of EPN with OBD nuclear dissipation in the first phase of nuclear fission, but the rule does not been exhibited because that there is abnormal enhancement of TDF using SPS nuclear dissipation. The increment of EPN caused by the rise of fission barrier is countered by the competition between TDF and nuclear damping in the second phase of nuclear fission, hence the effect of EPN cannot exhibit. The effect of DDSC on EPN near the neutron 126 closure-shell is dominated by the rules in the first phase of nuclear fission. -
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