摘要
利用三维经典系综模型系统地研究了不同强度线偏振激光脉冲驱动下He原子的非次序双电离.结果表明在非次序双电离中回碰电子的返回次数、两电子的碰撞距离和电子对的关联特性都强烈地依赖于激光强度.对于750 nm,随着激光强度的增加,单次返回诱导的非次序双电离事件逐渐减少,而多次返回事件的比例显著增加.对于1500 nm,随着激光强度的增加,前三次返回诱导的非次序双电离事件都会减少,返回次数大于3的轨道对非次序双电离的贡献逐渐增加.这是因为在高强度下每次返回过程中母核的库仑吸引对返回电子横向偏离的补偿较弱,所以需要更多次的返回来补偿电子的横向偏离以实现再碰撞.轨道分析表明非次序双电离中两电子的碰撞距离随激光波长和强度的增加而逐渐减小.最后讨论了非次序双电离中电子对的关联特性对返回次数的依赖.
Using the three-dimensional classical ensemble model,we systematically investigate the strong-field nonsequential double ionization(NSDI)of He atom by intense linearly polarized laser pulses at different intensities for 750 nm and 1500 nm in wavelength.In the intensity range of 0.4-0.8 PW/cm2 considered in this work,for 750 nm wavelength the correlated electron pairs are always distributed mainly near the diagonal but for 1500 nm wavelength,with increasing laser intensity the population of electron pairs moves from the diagonal to the two axes,forming a near-axis V-shaped structure at 0.8 PW/cm2.The analysis indicates that for 750 nm with increasing laser intensity the contribution from the single-return events to NSDI decreases sharply and the contribution from the multiple-return events increases.For 1500 nm wavelength when the laser intensity increases,the contributions from one-,two-and three-return trajectories decrease and the contributions of other trajectories increase.It is because most of ionized electrons have a non-zero initial transverse momentum.After the excursion of the ionized electron,when it returns to the parent ion at the first time there is a distance in the transverse direction between the free electron and the parent ion,which hinders the recollision and NSDI from occurring.The transverse deviation can be significantly reduced by the Coulomb attraction from the parent ion to the free electron when it returns back to the parent ion in the longitudinal direction.Higher intensity results in larger returning velocity for the free electron.The free electron faster passes by the parent ion and the Coulomb attraction has less time to pull the free electron to the parent ion.For each return the compensation of the Coulomb attraction for the transverse deviation for high intensity is weaker than for low intensity.Thus for higher intensities more returns are required to compensate for the transverse deviation.Moreover,numerical results show the recollision distance in NSDI is smaller for the longer
作者
黄诚
钟明敏
吴正茂
Huang Cheng;Zhong Ming-Min;Wu Zheng-Mao(School of Physical Science and Technology,Southwest University,Chongqing 400715,China)
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2019年第3期138-145,共8页
Acta Physica Sinica
基金
国家自然科学基金(批准号:11504302
61178011
61475127
61475132)资助的课题~~
关键词
非次序双电离
电子关联
强激光场
再碰撞
nonsequential double ionization
electron correlation
strong laser field
recollision
