Angular momentum distribution of atomic hydrogen in excited states under ultra-short laser field

We investigate the population distribution of excited angular momentum (l) states in the interaction between a hydrogen atom and an ultra-short laser pulse. Through numerical solution of the time-dependent Schrödinger equation, we theoretically investigate the laser-induced oscillations among excited l-states. Temporal evolution analysis reveals distinctive signatures of both multiphoton excitation and frustrated tunneling ionization processes. Specifically, multiphoton excitation dominates during the final optical cycle as the laser peak intensity attenuates, thereby critically determining the final l-states population distribution. We demonstrate that the angular quantum states’ parity effect does not persist, even for ultra-short pulses with broad frequency bandwidths. The parity effect is also unaffected by laser field asymmetry.