低于再碰撞阈值下强激光场原子非序列双电离(英文)

STRONG FIELD DOUBLE IONIZATION OF ATOMS BELOW THE RECOLLISION THRESHOLD

在最近的实验和理论研究中,我们探讨了氩原子和氖原子在红外强激光场中低于再碰撞阈值的非序列双电离问题。在研究中,我们发现在非序列双电离过程中,氖原子的电子关联表现为在激光偏振面内肩并肩出射,而对于氩原子的电子关联行为表现为在激光偏振面内的背对背出射,我们采用三维半经典模型(考虑电子隧道电离)很好地解释了实验结果。在阈值附近,我们发现电子在激光场中的多次散射以及电子再碰撞激发后电子隧道电离是氩原子反关联行为的主要原因,而电子在激光场作用下的单次碰撞是电子关联行为的主要原因。通过测量双电离过程中产生电子的横向电子动量分布,观察到了库伦聚焦效应,我们认为这是非经典的关联行为。最后,我们给出了氩原子和氖原子在激光场中阈值的解析模型,并给出了原子的关联和反关联激光强度区域。

In recent experimcntal and theoretical studics we explore non-sequential double ionization （NSDI） of Ne and Ar in the infrared light field below the recollision threshold. Very basic differences are found in the two-electron correlation momenta ＂side-by-side emission＂ （correlation） for Ne and ＂back-to-back emission＂ （anticorrelation） for Ar--that can be partially explained theoretically within our three dimensional classical model including tunneling. In the threshold regime, the multiple recol- lisions as well as recollision induced excitation tunneling dominates the anticorrclation of Ar, whereas the singly laser-assisted recollision dominates the correlation of Ne. We explored the transverse electron momentum distributions from double ionization of atoms providing insight into ＂Coulomb focusing＂ and pointing to correlated non-classical dynamics. Finally, classical strong-field double ionization threshold intensities, correlation as well as anticorrelation regimes are predicted for both atomic targets.