Monitoring the ultrafast buildup of Rabi oscillations in the time domain
Xu Zhang, Yijie Liao, Yongkun Chen, Yu Miao, Siyu Li, Mingrui He, Kunlong Liu, Peixiang Lu, Yueming Zhou
Abstract
We theoretically study the buildup of Rabi oscillations in the two-photon ionization process in atomic Hydrogen, where both resonant and nonresonant ionization paths play a significant role. Using spectrally and angularly resolved electron interferometry, we reconstruct the temporal profiles of electron wave packets (EWPs) and the time evolution of photoelectron energy spectra (PESs) for the $s$ and $d$ partial waves from the numerical results of time-dependent Schr\"odinger equation. Our results reveal the differences between the $s$ and $d$ waves in terms of the minimum of the temporal EWPs and the asymmetry of the time-evolving PESs. Based on a three-level model, we attribute these phenomena to the different contributions of the nonresonant path in these two partial waves. Further, with this model we highlight the opposite effects of the AC-Stark effect on resonant and nonresonant paths. Our work directly reveals the time-varying influence of the oscillating populations on the dynamics of resonant and nonresonant paths, and provides a feasible method for assessing the partial-wave resolved contribution of the nonresonant path in the time domain.