Precollision effect on the double ionization of an Ar atom driven by a two-color counter-rotating circularly polarized laser pulse

Abstract

The double ionization process of an Ar atom driven by a two-color counter-rotating circularly polarized (TCCP) laser pulse is theoretically investigated. Classical trajectory analysis reveals that a significant portion of Nonsequential Double Ionization (NSDI) events occurs through precollision, rather than the well-known recollision mechanism. In the precollision-induced Nonsequential Double Ionization (PCDI) process, the two electrons exhibit a tendency for back-to-back emission, resulting in a lower electronic correlation effect, and the ion recoil momentum concentrated in the zero momentum region. On the other hand, in the recollision-induced Nonsequential Double Ionization (RCDI) process, the two electrons tend to emit in the same direction, leading to a higher electronic correlation effect, and the ion recoil momentum is situated far from the zero momentum region. Moreover, both PCDI and RCDI strongly depend on the parameters of the driving laser pulse. Therefore, the primary mechanism of double ionization can be experimentally probed by observing the corresponding ion recoil momentum.