Q值效应对多核子转移反应136Xe+208Pb的影响

基于改进的量子分子动力学(ImQMD)模型，模拟了136Xe+208Pb在质心系入射能量为$E_{\rm{c.m.}}$=617 MeV的多核子转移反应。为了研究这个特殊的反应体系，将不同核子数转移前后形成的类弹与类靶对应的$Q$值的指数概率分布引入模型中考虑$Q$值效应，并将计算结果与实验探测的总动能损失分布和质量分布进行了比较。我们发现考虑$Q$值效应后的计算结果更好地再现了实验数据。在少于10个核子的转移过程中，核子的转移明显受到了$Q$值效应的驱动。在更多的核子转移过程中，$Q$值效应明显压低了反应产物的生成截面。这是因为大量的核子转移主要发生在小碰撞参数，对应的复合体系的寿命由于$Q$值效应明显减小。在ImQMD与ImQMD+Q的计算结果比较中，我们还发现，$Q$值效应明显增加了比208Pb更丰中子的中子数为126的初级碎块生成截面。

Effect of Q-value on Multinucleon Transfer Reaction 136Xe+208Pb

Multinucleon transfer reaction 136Xe+208Pb at $E_{\rm{c.m.}}$=617 MeV is simulated by improved quantum molecular dynamics (ImQMD) model with and without considering the effect of $Q$-value. The calculation results of ImQMD including the effect of $Q$-value (ImQMD+$Q$) generally better reproduce the experimental mass distribution and distribution of total kinetic energy lost (TKEL). $Q$-value effect is found to drive the transfer of less than ten nucleons and suppress more nucleons transfer. It also decreases the average lifetime of composite systems in the events at lower impact parameters. In the production of more neutron-rich isotopes with neutron number $N$=126, $Q$-value effect enhances the cross sections for these isotopes in the comparison between the results of ImQMD and ImQMD+$Q$.