Intrinsic resonant photoionization time delay of hydrogen atoms probed with attosecond beating of asymmetrical photon transitions

We investigate the benchmark photoionization of hydrogen atoms triggered by the third harmonic at vacuum ultraviolet laser pulses (at 202 nm) and probe the time delay via resonant quantum states with the weak fundamental laser pulses (at 606 nm). As a result, two different sidebands will emerge below the first above threshold ionization peak. We show that these two sidebands can be established through resonance with the 3d and 2p states of hydrogen atoms at 202 nm, respectively. Using this scheme, we can extract the angularly dependent time delay of electrons liberated from the 3d state with respect to those released from the 2p state by comparing the phase differences between two sidebands. Using the attosecond beating scheme of asymmetrical photon transition, we obtain the intrinsic time delay between the 3d and 2p excited electronic states in the few-photon ionization regime of H atoms, which is similar to 103 as. This asymmetric attosecond beating metrology provides insight into electron dynamics of the multiphoton resonant ionization via multi-intermediate states.

Automated summary

This study investigates benchmark photoionization of hydrogen atoms triggered by vacuum ultraviolet and weak fundamental laser pulses, probing time delay via resonant quantum states. Two different sidebands are established through resonance with the hydrogen atom's 3d and 2p states. By comparing phase differences between two sidebands, the angularly dependent time delay of electrons liberated from different states can be extracted. Using the asymmetric attosecond beating scheme, the intrinsic time delay between the 3d and 2p excited electronic states in the few-photon ionization regime of H atoms is determined to be around 103 as.