Coulomb and polarization effects in sub-cycle dynamics of strong-field ionization

Smirnova, Olga; Spanner, Michael; Ivanov, Misha

doi:10.1088/0953-4075/39/13/s05

Cited by 94 publications

(72 citation statements)

References 48 publications

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“…III A, we can approximate the boundary term B(a, θ , φ , t ) as in Eq. (17). This follows from the foresight that when we use the saddle point for the time integral, we end up with studying the dynamics of the wave function around the pole v(t s ) = iκ in the momentum space.…”

Section: The Wave Functionmentioning

confidence: 99%

Nonadiabatic Coulomb effects in strong-field ionization in circularly polarized laser fields

2013

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We develop the recently proposed analytical R-matrix (ARM) method to encompass strong field ionization by circularly polarized fields, for atoms with arbitrary binding potentials. Through the ARM method, the effect of the core potential can now be included consistently both during and after ionization. We find that Coulomb effects modify the ionization dynamics in several ways, including modification of (i) the ionization times, (ii) the initial conditions for the electron continuum dynamics, (iii) the "tunneling angle," at which the electron "enters" the barrier, and (iv) the electron drift momentum. We derive analytical expressions for the Coulomb-corrected ionization times, initial velocities, momentum shifts, and ionization rates in circularly polarized fields, for arbitrary angular momentum of the initial state. We also analyze how nonadiabatic Coulomb effects modify (i) the calibration of the attoclock in the angular streaking method and (ii) the ratio of ionization rates from p − and p + orbitals, predicted by I. Barth and O. Smirnova [Phys. Rev. A 84, 063415 (2011)] for short-range potentials.

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Section: The Wave Functionmentioning

confidence: 99%

Nonadiabatic Coulomb effects in strong-field ionization in circularly polarized laser fields

2013

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“…For SW-SFA, the agreement is not as good, but the improvement over SFA is still significant. The phase in SFA (or SW-SFA) can probably be improved by adding some correction to the semi-classical action, for example, as has been suggested [14,15]. At present, it is better to extract the phase of the wave packet from the companion atomic target where TDSE calculations can be carried out.…”

Section: First Inmentioning

confidence: 99%

Extraction of the species-dependent dipole amplitude and phase from high-order harmonic spectra in rare-gas atoms

Morishita

Lin

2008

Phys. Rev. A

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Based on high-order harmonic generation (HHG) spectra obtained from solving the timedependent Schrödinger equation for atoms, we established quantitatively that the HHG yield can be expressed as the product of a returning electron wave packet and the photo-recombination cross sections, and the shape of the returning wave packet is shown to be largely independent of the species. By comparing the HHG spectra generated from different targets under identical laser pulses, accurate structural information, including the phase of the recombination amplitude, can be retrieved. This result opens up the possibility of studying the target structure of complex systems, including their time evolution, from the HHG spectra generated by short laser pulses.PACS numbers: 42.65. Ky, 33.80.Rv When an atom is subjected to a strong driving laser field, one of the most important nonlinear response processes is the generation of high-order harmonics. In the past decade, high-order harmonic generation (HHG) has been used for the production of single attosecond pulses [1,2,3] and attosecond pulse trains [4], thus opening up new opportunities for attosecond time-resolved spectroscopy. HHG is understood using the three-step model (TSM) [5,6,7] -first the electron is released by tunnel ionization; second, it is accelerated by the oscillating electric field of the laser and later driven back to the target ion; and third, the electron recombines with the ion to emit a high energy photon. A semiclassical formulation of the TSM based on the strong-field approximation (SFA) is given by Lewenstein et al [7]. In this model (often called Lewenstein model), the liberated continuum electron experiences the full effect from the laser field, but not from the ion that it has left behind. In spite of this limitation, the SFA model has been used quite successfully, in particular, for analysis of the attosecond synchronization of high harmonics, see Mairesse et al [8] and references therein. However, since the continuum electron recombines when it is near the parent ion, the neglect of electron-ion interaction in the SFA model is rather questionable.According to the TSM, the last step of HHG is analogous to the radiative recombination process in electronion collisions. Thus one may write the HHG signal aswhere d(ω) is the photo-recombination (PR) transition dipole and W (E) is the returning "electron wave packet". Electron energy E is related to the emitted photon energy ω by E = ω − I p , with I p being the ionization potential of the target. Clearly the HHG signal S(ω) and W (E) depend on the laser properties. On the other hand, d (ω) is the property of the target only. The factorization in Eq. (1) is most useful when one compares the HHG spectra from two different targets in the identical laser field. Assuming that the shape of W (E) is species independent, by measuring the relative HHG yields, one can deduce the PR cross section of one species if the PR cross section of the other is known. The validity of Eq. (1) has been shown recently in Morishit...

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“…Therefore, its trajectory, for the most part, is that of a free electron in an external electric field which can be described by Volkov states (plane waves with time-dependent momentum) [12]. The basic assumptions of SFA are (a) neglect the laser field for the calculation of bound states, and (b) neglect the core Coulomb potential for the calculation of the continuum states [13]. A recently measured HHG spectrum of Ar is shown to have a deep minimum (related to the Cooper minimum of its photoelectron spectrum) that is independent of the laser intensity or wavelength [14,15].…”

Section: Introductionmentioning

confidence: 99%

Recombination-amplitude calculations of noble gases, in both length and acceleration forms, beyond the strong-field approximation

et al. 2013

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Transition of an electron from a free to a bound state is critical in determining the qualitative shape of the spectrum in high-order-harmonic generation (HHG), and in tomographic imaging of orbitals. We calculate and compare the recombination amplitude, from a continuum state described by a plane wave and an outgoing scattering eigenstate, to the bound state for the noble gases that are commonly used in HHG. These calculations are based on the single active electron model and the Hartree-Fock-Slater method, using both the length form and the acceleration form of the dipole matrix element. We confirm that the recombination amplitude versus emitted photon energy strongly depends upon the wave function used to describe the free electron. Depending on the choice of the wave function and the dipole form, the square of the absolute value of the recombination amplitude can differ by almost two orders of magnitude near the experimentally measured Cooper minima. Moreover, only the outgoing scattering eigenstates with the length form roughly predict the experimentally observed Cooper minimum for Ar (∼50 eV) and Kr (∼85 eV). We provide a detailed derivation of the photorecombination cross sections from photoionization cross sections (PICSs) calculated by the relativistic random phase approximation (RRPA). For Ar, Kr, and Xe, we compare the total PICSs calculated using our recombination amplitudes with that obtained from RRPA. We find that PICS calculated using the outgoing scattering eigenstates with the length form is in better agreement with the RRPA calculations than the acceleration form.

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Coulomb and polarization effects in sub-cycle dynamics of strong-field ionization

Cited by 94 publications

References 48 publications

Nonadiabatic Coulomb effects in strong-field ionization in circularly polarized laser fields

Nonadiabatic Coulomb effects in strong-field ionization in circularly polarized laser fields

Extraction of the species-dependent dipole amplitude and phase from high-order harmonic spectra in rare-gas atoms

Recombination-amplitude calculations of noble gases, in both length and acceleration forms, beyond the strong-field approximation

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