Influence of multiphoton resonance excitation on the above-threshold ionization of a hydrogen atom

The photo-electron emission of a hydrogen atom irradiated by an ultraviolet laser pulse is investigated by numerically solving the time-dependent Schrodinger equation in momentum space. A subpeak structure with high intensity is observed in the photo-electron emission spectrum, and the peak of the enhanced structure shifts to a higher energy as the laser intensity increases. Through the strong-field approximation and the analysis of the population of the bound state, it is found that this subpeak structure is generated from the interference between the ionized electrons from the ground state and the ionized electrons from the 2p state after the resonant transition from the ground state to the 2p state. Analyzing the change rule of the photo-electron emission spectrum can further deepen the understanding of the energy change of the dressed bound state for an atom irradiated by an intense laser pulse. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement