Trajectory selection using XUV pulses in nonsequential double ionization

Motivated by recent experiments on trajectory selection in nonsequential double ionization (NSDI) [A. Piper et al., PRL 134, 073201 (2025)], we present a time domain model for NSDI induced by extreme ultraviolet (XUV) photons in helium in the presence of a strong, synchronized infrared (IR) field. Using a 1+1D time-dependent Schrödinger equation (TDSE) model, we apply an XUV pulse to excite or ionize an electron at a chosen time within the IR cycle by scanning the relative delay between the XUV and IR fields. We then document how the IR field steers the photoelectron wave packet to realize distinct pathways leading to NSDI. From our calculations, we extract the double ionization yield and time-resolved electron dynamics to quantify the efficiency of different NSDI trajectories, optimize the trajectory selection protocol, compare direct and resonantly enhanced NSDI, and determine how the dominant pathway depends on the relative XUV-IR delay.