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  • Letter
  • Open Access

Quantitative analysis of resonant ionization by smooth laser pulses: Connection between effective Hamiltonian theory and strong-field dressed continua

Jakob Nicolai Bruhnke and Jan Marcus Dahlström*

  • *Contact author: marcus.dahlstrom@fysik.lu.se
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Phys. Rev. Research 8, L032041 – Published 10 September, 2026

DOI: https://doi.org/10.1103/lnbk-npp9

Abstract

Resonant photoionization in the intense high-frequency regime can exhibit extremely asymmetric Autler-Townes doublets whose origin remains debated. It has been attributed either to interference between perturbative ionization pathways or to a nonperturbative dressing of the continuum. Here, we show that these interpretations arise from a common effective Hamiltonian framework, in which dressed-state stabilization is governed by the coherent interplay of resonant and nonresonant pathways. We demonstrate that further simplification, using the strong-field approximation, obscures this mechanism. In contrast, our time-dependent essential-state model, where electrons are rigorously coupled to the continuum, achieves excellent agreement with ab initio simulations of the time-dependent Schrödinger equation for helium.

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Phys. Rev. Research 8, L032041– Published 10 September, 2026
  • Received 31 March 2026
  • Accepted 20 August 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by Bibsam.

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