Threshold effects in strong-field ionization: Energy shifts and Rydberg structures

Krajewska, K.; Fabrikant, I. I.; Starace, Anthony F.

doi:10.1103/physreva.86.053410

Cited by 18 publications

(18 citation statements)

References 44 publications

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“…For comparison, we also show the probability of ionization in the adiabatic limit. The behavior of the ionization probability is very similar to the behavior of the ionization rate evaluated within Floquet theory [19,20] with one striking difference. According to Floquet theory, the ionization potential and therefore the number of photons required to ionize the atom increases with peak intensity due to the AC-Stark shift of the atomic levels.…”

Section: Resultssupporting

confidence: 59%

“…(1)), the behavior of the ionization probability is qualitatively similar : a smooth region followed by a region of isolated (Freeman type) resonances and a broad hilly structure. However, in [19,20], it was shown that the behavior of the ionization rate is nearly constant just below and above each N-photon threshold. This contrasts with the behavior of the ionization probability shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

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Excitation of Rydberg wave packets in the tunneling regime

et al. 2017

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In the tunneling regime for strong laser field ionization of atoms, experimental studies have shown that a substantial fraction of atoms survive the laser pulse in many Rydberg states. To explain the origin of such trapping of population into Rydberg states, two mechanisms have been proposed : the first involves AC-Stark-shifted multiphoton resonances and the second, called frustrated tunneling ionization, leads to the recombination of tunneled electrons into Rydberg states. We use a very accurate spectral method based on complex sturmian functions to solve the time dependent Schrödinger equation for hydrogen in a linearly polarized infrared pulse and to calculate the tunneling probability in terms of the atomic ground state width. We examine the probability of excitation into Rydberg states as a function of the peak intensity for various pulse durations and two wavelengths, 800 nm and 1800 nm and try to explain the results in light of the two aforementioned mechanisms. For long pulses of 800 nm wavelength, the extreme sensitivity of the trapping of population into high-lying Rydberg states to the peak intensity, the well defined value and parity of the angular momentum of the populated Rydberg states and the presence of Freeman resonances can be explained using a multiphotonic excitation mechanism. For strong pulses of 1800 nm wavelength, in the so-called adiabatic or quasi-static tunneling regime, the oscillations of the excitation probability as a function of intensity are in phase opposition to the ionization probability and we observe a migration towards high values of the angular momentum with different distributions in the angular momentum at the maxima and minima of the oscillations. We also present a detailed study of how the excited state wave packet builds up in time during the interaction of the atom with the pulse.

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Section: Resultssupporting

confidence: 59%

Section: Resultsmentioning

confidence: 99%

Excitation of Rydberg wave packets in the tunneling regime

et al. 2017

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“…[18], the positions of the maxima of these oscillations depend on the shape of the atomic potential: For a short-range potential they coincide with the positions of multiphoton thresholds [16], whereas the corresponding peaks for a Coulomb potential occur in the middle between two neighboring multiphoton thresholds [18]. (Similar features have been found in strongfield ionization of an electron in a Coulomb potential [21]). …”

Section: Introductionmentioning

confidence: 51%

Scaling laws for high-order-harmonic generation with midinfrared laser pulses

et al. 2015

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We derive an analytic expression for the wavelength scaling of the high-order-harmonic generation (HHG) yield induced by midinfrared driving laser fields. It is based on a quasiclassical description of the returning electron wave packet, which is shown to be largely independent of atomic properties. The accuracy of this analytic expression is confirmed by comparison with results of numerical solutions of the time-dependent Schrödinger equation for wavelengths in the range of 1.4 μm ≤ λ ≤ 4 μm. We verify the wavelength scaling of the HHG yield found numerically for midinfrared laser fields in a recent paper by Le et al. [Phys. Rev. Lett. 113, 033001 (2014)].

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“…Theoretical analysis of the angular momentum distribution in the populated Rydberg states is less advanced. Predictions of Floquet theory for a monochromatic laser field [35] and results of numerical calculations for laser pulses with a trapezoidal envelope [32] yield that the angular momentum of the excited Rydberg states has the same parity as N p − 1, where N p is the minimum number of photons needed to ionize the atom. Furthermore, the angular quantum number of the states with the largest population in numerical calculations [9,10,32] agrees well with semiclassical estimations [36], initially performed for low-energy angular resolved photoelectron distributions.…”

Section: Introductionmentioning

confidence: 99%

“…Recent theoretical studies of the excitation mechanism in strong fields mainly consider the distribution of the population as a function of the principal quantum number of the excited states [9,10,25,31,32]. It was shown that the modulation of the excitation probability is related to the channel closing effect [9,10,32,35]. The latter phenomenon occurs at threshold intensities at which the absorption of one more photon is needed to ionize the atom due to the shift of the ionization threshold by the ponderomotive energy.…”

Section: Introductionmentioning

confidence: 99%

Angular momentum distribution in Rydberg states excited by a strong laser pulse

et al. 2018

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We study the excitation to Rydberg states in the interaction of the hydrogen atom with a short strong laser pulse. Utilizing solutions of the time-dependent Schrödinger equation we find that the parity of the populated angular momentum states agrees with the selection rules for multiphoton resonant absorption at low intensities, if the pulse length is not too short. In contrast, the parity effect cannot be observed for ultrashort pulses as well as for long pulses at high intensities. We further identify signatures of the population in the excited states via the line emissions from the populated np states after the end of the pulse exhibiting the parity effect.

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Threshold effects in strong-field ionization: Energy shifts and Rydberg structures

Cited by 18 publications

References 44 publications

Excitation of Rydberg wave packets in the tunneling regime

Excitation of Rydberg wave packets in the tunneling regime

Scaling laws for high-order-harmonic generation with midinfrared laser pulses

Angular momentum distribution in Rydberg states excited by a strong laser pulse

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