Exploring the role of chaos in model recollision processes.

The physics of particle recollisions offers a window into the complex dynamics of interactions between charged particles and external fields. While simple classical models often describe these recollisions by focusing on the motion driven by an external field alone, e.g., the three-step model in high harmonic generation, this assumption excludes the possibility of chaotic behavior. In this work, we explore how chaotic motion emerges in recollision processes by including the strength of the Coulomb potential as a parameter. Through a continuous scan of system parameters, we uncover the transition from regularity to chaos. Interestingly, we find a transition from regular to chaotic to regular motion as a function of the 2D scan of Coulomb strength and field strength. In addition, scanning over the initial phase of the driving field allows us to identify the sensitive dependence on initial conditions characteristic of chaotic motion. Our findings reveal that the system can exhibit chaotic dynamics on timescales much longer than the initial recollision.