Probing the dynamics of autoionizing states with Raman electron interferometry

Traditional pump-probe photoelectron wavepacket interferometry employs a broadband pulse to prepare a wavepacket and a delayed ionizing probe to produce quantum beats between overlapping pathways in the continuum. The kinetic energy resolution is however constrained by the probe pulse duration. We report an alternate approach that allows for both high temporal and spectral resolution by stimulating Raman transitions with one pulse and monitoring the differential changes in electron yield via delayed autoionization. We applied this new method to study the autoionizing wavepackets excited between the spin-orbit split ionization threshold of argon and obtained remarkable agreement with theoretical calculations. We extended this new method to study the autoionization dynamics in other atomic and molecular systems. Additionally, we report progress on the time and energy dependence of the photoelectron angular distribution parameters to understand the distinct phase relationship between signals from two ion core channels in argon. Experimental results are compared with multichannel quantum defect theory calculations to highlight the importance of many-electron interactions in photoionization.