中文摘要：

利用LAMMPS程序研究了氢原子团簇在飞秒强激光场下的动力学行为,讨论了引起小氢原子团簇各向异性膨胀的原因.通过对外电离过程中团簇内部电子的行为以及团簇各个方向上最外层质子距离团簇中心的距离随时间的变化情况的分析,发现团簇的膨胀呈现各向异性,且引起这种各向异性的根源在于团簇内部电子的抖动以及逃逸.对氢原子团簇与强激光场相互作用过程中质子各能量分量以及各向异性程度随时间变化情况进行了研究,发现各向异性程度是随时间变化的,这种各向异性程度首先随着激光电场的增强而增加,随后又逐渐减小,直到最后趋于某一大于1的稳定值.分析了激光脉冲结束后质子的平均能量与观测角之间的关系,并将分析结果与Ditmire小组的实验结果进行了比较,发现我们的模拟结果在定性上与实验相符合.

英文摘要：

In this paper,a simulation discussing the cause inducing the anisotropy of hydrogen cluster expansion is implemented by using LAMMPS tool for the molecule dynamics simulations.Through analyzing the behavior of electrons contained in the cluster and the variations of distance between outermost protons of all directions and cluster center with time,we clearly find that the expansion of hydrogen cluster is anisotropic,which is due mainly to the anisotropies of the quiver and escaping of electrons.Then we study the evolutions of proton energy component and anisotropic degree,and find that the anisotropic degree first increases with laser electric field increasing,then decreases gradually to a stable value greater than one.Additionally,we analyze the relationship between observation angle and average proton energy from hydrogen cluster irradiated by ultreshort laser pulse,and find that our simulation results accord with the experimental results qualitatively.