Effect of nonresonant states in near-resonant two-photon ionization of hydrogen

Zhang, Xu and Zhou, Yueming and Liao, Yijie and Chen, Yongkun and Liang, Jintai and Qinghua, Ke and Min, Li and Csehi, András and Peixiang, Lu (2022) Effect of nonresonant states in near-resonant two-photon ionization of hydrogen. PHYSICAL REVIEW A, 106 (6). ISSN 2469-9926

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Abstract

By numerically solving the three-dimensional time-dependent Schr¨odinger equation, two-photon ionization of Hydrogen is investigated at the near-resonant frequencies of the 1s-2p transition. Due to the Rabi oscillations between the 1s and 2p states, the photoelectron energy spectra exhibit the Autler-Townes (AT) doublets and we focus on the energy spacing and the asymmetry of the doublets. Our results show that the laser frequency for the minimum energy spacing of AT doublets locates at the resonant frequency of the ac-stark shifted states, while the symmetry of the AT doublets is affected both by the ac-stark shift and the non-resonant ionization pathway. Developing the minimal three-state model including all of the non-resonant (non-essential) states , the effects of the ac-stark shift and the non-resonant ionization pathway on the AT doublets due to the non-resonant states are identified. Furthermore, due to non-resonant ionization pathway, the photoelectron angular distributions are distinctly different for the lower and higher energy peaks in the AT doublets, and these angular distributions sensitively depend on the laser intensity and pulse duration. These results are well reproduced by our minimal three-state model.

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