基于经典系综模型,研究了Mg原子在低于重碰撞阈值激光功率密度下的非序列双电离(NSDI)。当少周期量级线性偏振激光的功率密度为3.0×10 ¹³ W·cm ^-2时,末态关联电子动量分布中的电子对主要分布在第一、第二和第四象限,第一象限中的电子对呈现了明显的关联行为。分析了重碰撞和双电离之间的延迟时间,发现不同的延迟时间对应着不同的电离过程,延迟时间对电子出射过程具有显著影响;延迟时间小于半个周期的NSDI事件,双电子倾向于反方向出射,而延迟时间大于半个周期的,存在双电子同方向出射的可能。

The nonsequential double ionization (NSDI) of Mg atoms below the recollision threshold laser power density is investigated based on the classical ensemble model. For a few-cycle linearly polarized laser pulses with a power density of 3.0×10 13 W·cm -2, the electron pairs in the correlated-electron momentum distribution at a final state mainly locate in the first, second and fourth quadrants. Moreover, the electron pairs in the first quadrant show an obvious correlation behavior. By analyzing the delay time between the recollision and the double ionization, it is found that the different delay time corresponds to different ionization processes and the delay time plays an important role in the process of the electron emission. For the NSDI events with delay time less than a half cycle, two electrons tend to emit with an opposite direction, however, for those with delay time larger than a half cycle, there exist emission electrons with the same direction.