Energy, angle, and time-resolved probing of electron wavepacket dynamics with attosecond pulse trains and tunable laser pulses

We study the photoionization dynamics in atoms and molecules using tunable infrared laser pulses in conjunction with extreme ultraviolet (XUV) attosecond pulse trains. XUV excites a Rydberg wavepacket and delayed IR probe ionizes to produce photoelectrons which are analyzed in a time and angle resolved fashion with a velocity map imaging spectrometer. In argon, the tunable IR wavelength is used to control the outgoing electron energy relative to the two spin-orbit split ionization thresholds to investigate the contributions of different angular momentum states. We observed quantum beating in the delay-dependent yield for both ionization thresholds, albiet with a distinct phase difference between the two channels. The results are interpreted with a multi-channel quantum defect analysis of different pathways, which highlights importance of many-electron interactions in photoionization. The time and energy dependence of beta parameters is also analyzed in argon as well as other atomic and molecular systems.