https://doi.org/10.1140/epjd/s10053-022-00572-7
Regular Article – Ultraintense and Ultrashort Laser Fields
Analysis of the asymmetry of Autler–Townes doublets in the energy spectra of photoelectrons produced at two-photon ionization of atoms by strong laser pulses
Institute of Physics, University of Belgrade, Pregrevica 118, 11080, Belgrade, Serbia
Received:
1
November
2022
Accepted:
29
November
2022
Published online:
21
December
2022
We analyzed the asymmetry of Autler–Townes doublets in the calculated photoelectron energy spectra for the two-photon ionization of the hydrogen atom by an intense short laser pulse that resonantly couples its ground state with the excited 2p state. The spectra are calculated applying the method of time-dependent amplitudes using two approaches of different level of approximation. The first approach involves solving a complete set of equations for amplitudes, which, in addition to amplitudes of coupled (1s, 2p) and continuous states, also includes the amplitudes of other discrete (nonessential) states. The second approach is the three-level model that includes only the amplitudes of the two coupled states and those of continuum states. By comparing the spectra obtained using these two approaches it is confirmed that the shift of the Autler–Townes doublets, which exists only in the spectra obtained by solving the full set of equations, can be attributed to the AC Stark shift, which is a consequence of the coupling with nonessential states. Finally, it was found that the asymmetry in the intensity of the Autler–Townes doublet components, which appears in the spectra obtained using both computational approaches, is primarily due to the decrease in the transition probability between the 2p and continuum states with increasing photoelectron energy.
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© The Author(s), under exclusive licence to EDP Sciences, SIF and Springer-Verlag GmbH Germany, part of Springer Nature 2022. Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
