碰撞阈值下氩原子非次序双电离

摘要

利用三维经典系综模型研究了碰撞阈值下氩原子的非次序双电离.计算结果表明,关联电子末态纵向动量主要分布在二、四象限,且在原点附近几乎没有分布;Ar2+离子末态纵向动量谱在零动量附近呈单峰结构.上述结果与实验结果[Phys.Rev.Lett.101 053001(2008)]定量一致.轨迹分析表明,在碰撞阈值下,氩原子非次序双电离的微观物理机理在不同激光强度下是不相同的.当激光强度I=0.7 ×1014 W/cm2时,一次碰撞主导重碰撞过程.而当I=0.4×1014W/cm2时,多次碰撞占主导.另外,离子与电子之间的库仑引力,在氩原子非次序双电离过程中具有重要的作用,对电子的微观动力学行为有很大的影响,并最终影响关联电子末态动量分布.%Nonsequential double ionization (NSDI) of Ar atom below the recollision threshold is investigated using the threedimensional classical ensembles. The calculated results reveal a dominance of events for electron emission into opposite hemispheres, a clear minimum of the correlated electron-electron momentum distributions at the origin and a single peak structure of the Ar2+ ions longitudinal momentum spectra near zero momentum. The momentum spectra of the Ar2+ ions agree with the experimental results [ Phys. Rev. Lett. 101 053001 (2008) ] quantitatively. Trajectoryback analyses show that the microscopic physical mechanisms of Ar NSDI are distinct for different intensities of the laser. When laser intensity equal to 0. 7 × 1014 W/cm2 , one recollision dominates the process of the recollision. However, the domination convert to multiple recollisions as the laser intensity decreases to 0.4 × 1014 W/cm2. In addition, the Coulomb attraction between the ion and electron plays an important role in microscopic dynamics of the electron in the process of Ar NSDI and eventually influences the final-state correlated electron-electron momentum distributions strongly.