Studying few-photon ionization dynamics in continuous pump-probe experiments

Cold Target Recoil Ion Momentum Spectroscopy (COLTRIMS) is a powerful tool for studying atomic photoionization by capturing photoelectron angular and energy distributions. However, it is mainly limited to pulsed light sources, where precise timing is crucial for reconstructing fragment dynamics. With continuous wave (cw) lasers, time-of-flight information is lost, making 3D momentum reconstruction impossible. We present a method extending COLTRIMS to analyze atomic photofragmentation from cw lasers, applied to few-photon ionization of 6Li atoms. In one experiment, atoms in optically pumped 2²S_1/2 and 2²P_3/2 states within an all-optical trap undergo resonance-enhanced two-color three-photon ionization, revealing polarization-dependent pathways. In another, multi-photon excitation with a femtosecond laser populates a Rydberg wave packet, followed by infrared ionization in an optical dipole trap. This technique enables evaluation of cascade dynamics and direct observation of time-dependent Rydberg wave packet evolution. It lays the groundwork for future studies on photoionization using laser fields with helical wavefronts, potentially enabling control of electron dynamics through angular momentum transfer.