Laser‑stabilised ionising transitions
Laser‑stabilised ionising transitions
Stabilising atoms exposed to intense laser fields has been a central topic in atomic physics for decades, inspiring several theoretical frameworks that describe the phenomenon under different resonance conditions and coupling regimes. Here we theoretically investigate an ionising electronic transition driven by a resonant pump field, in contrast to Kramers–Henneberger atoms, which are stabilised by non-perturbative, non-resonant laser pulses. We show that, above a critical pump intensity, the drive creates a novel metastable electronic bound state embedded in the continuum, which decays via two-photon ionisation. We calculate the resulting resonant fluorescence spectrum and find a qualitatively different structure from the familiar Mollow triplet associated with bound-to-bound transitions. This fluorescence provides a time-resolved probe of the population of the metastable state. In analogy to how the AC Stark shift is a semiclassical counterpart of the single-photon Rabi splitting observed in optical cavities, the phenomenon we describe is best understood as a semiclassical analogue of recently observed excitons bound by a single cavity photon.
Cortese, Erika
3a7d67d1-3321-40b2-91fa-2471dbed7147
De Liberato, Simone
5942e45f-3115-4027-8653-a82667ed8473
Cortese, Erika
3a7d67d1-3321-40b2-91fa-2471dbed7147
De Liberato, Simone
5942e45f-3115-4027-8653-a82667ed8473
Cortese, Erika and De Liberato, Simone
(2025)
Laser‑stabilised ionising transitions.
Optica.
(In Press)
Abstract
Stabilising atoms exposed to intense laser fields has been a central topic in atomic physics for decades, inspiring several theoretical frameworks that describe the phenomenon under different resonance conditions and coupling regimes. Here we theoretically investigate an ionising electronic transition driven by a resonant pump field, in contrast to Kramers–Henneberger atoms, which are stabilised by non-perturbative, non-resonant laser pulses. We show that, above a critical pump intensity, the drive creates a novel metastable electronic bound state embedded in the continuum, which decays via two-photon ionisation. We calculate the resulting resonant fluorescence spectrum and find a qualitatively different structure from the familiar Mollow triplet associated with bound-to-bound transitions. This fluorescence provides a time-resolved probe of the population of the metastable state. In analogy to how the AC Stark shift is a semiclassical counterpart of the single-photon Rabi splitting observed in optical cavities, the phenomenon we describe is best understood as a semiclassical analogue of recently observed excitons bound by a single cavity photon.
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Accepted/In Press date: 2 December 2025
Identifiers
Local EPrints ID: 508178
URI: http://eprints.soton.ac.uk/id/eprint/508178
ISSN: 2334-2536
PURE UUID: 4edb3f7c-42c5-4cfa-b970-25841bd4d392
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Date deposited: 14 Jan 2026 17:36
Last modified: 15 Jan 2026 02:45
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