反旋双色椭圆偏振激光场中Ar原子的非序列双电离  

Nonsequential double ionization of Ar atoms in counter-rotating two-color elliptically polarized laser fields

作　　者：葛振杰 苏旭 白丽华[1] Ge Zhen-Jie;Su Xu;Bai Li-Hua(Department of Physics,College of Science,Shanghai University,Shanghai 200444,China)

机构地区：[1]上海大学理学院物理系,上海200444

出　　处：《物理学报》2024年第9期78-87,共10页Acta Physica Sinica

摘　　要：利用经典系综方法研究了不同椭偏率的反旋双色椭圆偏振(two-color elliptically polarized,TCEP)激光场中Ar原子非序列双电离(nonsequential double ionization,NSDI)的电子关联特性和再碰撞动力学.不同于反旋双色圆偏振激光场,反旋TCEP激光场不再具有空间对称性,返回电子主要从一个方向返回母离子,从而导致电子动量分布表现出很强的不对称性.数值结果显示随着椭偏率的增大,Ar原子NSDI的产量逐渐减小,并且电子对在椭圆偏振激光场长轴方向上的关联电子动量分布,从主要位于第一和第三象限的正相关逐渐演变为主要位于第二和第四象限的反相关.通过对不同特征时间的统计分析表明,随着椭偏率的增大,旅行时间和返回电子的重碰撞能量逐渐减小,而延迟时间却增大,这是电子对关联特性发生变化的主要原因.此外,进一步分析发现,无论是“短轨迹”还是“长轨迹”,椭偏率的增大都会使两个电子由同向出射逐渐转变为反向出射,这表明椭偏率和旅行时间都影响着电子的出射方向.Electron correlation behaviors and recollision dynamics in nonsequential double ionization(NSDI)of Ar atoms in counter-rotating two-color elliptically polarized(TCEP)laser fields are investigated by using the classical ensemble model.The combined electric field in counter-rotating TCEP laser pulses traces out a trefoil pattern,i.e.the waveform in a period shows three leaves in different directions,and each leaf is called a lobe.Unlike counter-rotating two-color circularly polarized laser field,the combined electric field has no spatial symmetry.The amplitudes of the three field lobes and the angles between them are different.Thus,the returning electron mainly returns to the parent ion from one direction,and the electron momentum distributions show strong asymmetry.Numerical results show that the NSDI yield gradually decreases as the ellipticity increases,and the correlated behavior of the correlated electron momentum along the long axis of the laser polarization plane gradually evolves from correlation behavior mainly located in the first quadrant and the third quadrant to anti-correlation behavior mainly located in the second quadrant and fourth quadrant.In order to further understand the correlation behaviors of electron pairs,different characteristic times in the NSDI processes are discussed,respectively.It is found that single ionization events and recollision events gradually decrease,but single ionization time and recollision time change slightly.This may be the main reason for the decrease in NSDI yield.And as the ellipticity increases,the traveling time and the recollision energy gradually decrease,while the delay time increases.Therefore,we can conclude that ellipticity may be responsible for the NSDI process.In addition,further analysis finds that the shape of the trajectory becomes more and more triangular as the ellipticity increases due to the counter-rotating TCEP laser fields of the specific dynamical symmetries of the total net electric field.And it is found that whether it is a“short trajectory

关 键 词：反旋双色椭圆偏振激光场 非序列双电离 椭偏率 电子关联 

分 类 号：O562.4[理学—原子与分子物理]