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A: Fachverband Atomphysik
A 13: Posters: Photoionization and atomic systems in external fields
A 13.6: Poster
Tuesday, March 11, 2008, 16:30–18:30, Poster C3
Resonant strong field ionization of atomic hydrogen — •Mircea G. Girju, Kiril Hristov, Oleg Kidun, and Dieter Bauer — Max Planck Institute for Nuclear Physics, Heidelberg, Germany
In H(1s) close to resonance with the 2p state Autler-Townes duplets are known to appear in the photoelectron spectra [1]. In the case of sufficiently weak laser fields the two peaks of each Autler-Townes pair are separated by Ω = √ΩR2+Δ2 with ΩR the Rabi-frequency and Δ the detuning. However, our numerical ab initio solutions of the time-dependent Schrödinger (TDSE) equation show that already at 1014 Wcm−2 the true peak separation deviates from the naively expected gap according to the above formula. The reasons for this failure are the use of the rotating wave approximation and the neglect of ionization, AC Stark effect, and other excited states.
A strong field approximation (SFA) is developed for an initially bound electron interacting with a resonant high-frequency pulse causing both Rabi-floppings and ionization. Taking the pure Rabi-flopping as the zeroth-order approximation in a straightforward two bound state-SFA turns out to yield inaccurate Autler-Townes peak strengths, the more so the larger the detuning | Δ| is [2].
[1] K.J. LaGattuta, Phys. Rev. A 47, 1560 (1993).
[2] M.G. Girju, K. Hristov, O. Kidun, and D. Bauer, J. Phys. B: At. Mol. Opt. Phys. 40, 4165 (2007).