少光周期的中红外激光脉冲驱动的Xe原子非次序双电离

Nonsequential Double Ionization of Xe Atoms Sriven by a Few-cycle Mid-infrared Laser Pulse

利用经典系综模型,系统研究了不同载波包络相位(Carrier-envelopphase,CEP)下少光周期的中红外激光脉冲驱动的Xe原子非次序双电离,并比较了近红外激光脉冲的情况。结果表明,中红外激光脉冲下,随CEP的增加,关联电子沿激光偏振方向的动量谱由分布在第一、二、四象限的弧形结构转变到主要分布在第一、三象限的弧形结构。而近红外激光脉冲下,关联电子动量谱由主要分布在第一、三象限的V型结构转变到主要分布在第一象限的V型结构。反演分析发现,中红外激光脉冲下,NSDI主要以直接碰撞电离机制主导,碰撞时间主要由位于激光场峰值附近的P1峰和位于激光场零点附近的P2峰贡献,P1峰导致关联电子动量谱在第一、二、四象限的弧形结构,P2峰导致关联电子动量谱在第一、三象限的弧形结构。进一步研究发现,对于中红外激光脉冲,根据双电离与碰撞之间的时间延迟进一步把NSDI事件分开,发现即使对于直接碰撞电离机制,不同的时间延迟范围内,电子关联特性仍呈现出不同的行为。

Using the classical ensemble model,the nonsequential double ionization of Xe atoms driven by a few-cycle mid-infrared laser pulse at different carrier-envelop phases(CEP)is systematically studied,and compared with near-infrared laser pulses.The results show that for a mid-infrared laser pulse,with increasing CEP the momentum spectrum of the correlated electrons along the laser polarisation direction changes from the arc-like structure distributed in the first,second and fourth quadrants to the arc-like structure mainly distributed in the first and third quadrants.However,in a near-infrared laser pulse,the momentum spectrum of the correlated electrons changes from being distributed in the first and third quadrants to a V-shaped structure mainly distributed in the first quadrant.The back analysis shows that the NSDI is mainly dominated by the recollision-impact ionisation mechanism in the mid-infrared laser pulse,and the collision time is mainly contributed by the P1 peak near the laser field peak and the P2 peak near the laser field zero.Peak P1 leads to the arc-like structure of the correlated electron momentum spectrum in the first,second and fourth quadrants,P2 leads to the arc-like structure of the correlated electron momentum spectrum in the first and third quadrants.The research shows that for the mid-infrared laser pulse,the NSDI events are further separated according to the time delay between the double ionisation time and the collision time.It is found that even for the recollision-impact ionisation mechanism,the correlation properties of the electron pairs still show different behaviour at different time delay ranges.