Exchange and polarization effect in high-order harmonic imaging of molecular structures

Sukiasyan, Suren; Patchkovskii, Serguei; Smirnova, Olga; Brabec, Thomas; Ivanov, Misha

doi:10.1103/physreva.82.043414

Cited by 45 publications

(50 citation statements)

References 86 publications

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“…(1). The MCTDHF method has, e.g., been applied to describe high-harmonic generation (HHG) in low dimensions [40], polarization of the continuum [41] and to calculate cross sections of atomic [38,42] and molecular systems [37]. Since the spatial orbitals are time-dependent, the one-and two-body operators must be updated at each time step, leading to a high numerical cost, especially in the 3D case.…”

Section: Introductionmentioning

confidence: 99%

Electron correlation in beryllium: Effects in the ground state, short-pulse photoionization, and time-delay studies

Omiste

Madsen

2017

Phys. Rev. A

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We apply a three-dimensional (3D) implementation of the time-dependent restricted-active-space self-consistent-field (TD-RASSCF) method to investigate effects of electron correlation in the ground state of Be as well as in its photoionization dynamics by short XUV pulses, including time-delay in photoionization. First, we obtain the ground state by propagation in imaginary time. We show that the flexibility of the TD-RASSCF on the choice of the active orbital space makes it possible to consider only relevant active space orbitals, facilitating the convergence to the ground state compared to the multiconfigurational time-dependent Hartree-Fock method, used as a benchmark to show the accuracy and efficiency of TD-RASSCF. Second, we solve the equations of motion to compute photoelectron spectra of Be after interacting with a short linearly polarized XUV laser pulse. We compare the spectra for different RAS schemes, and in this way we identify the orbital spaces that are relevant for an accurate description of the photoelectron spectra. Finally, we investigate the effects of electron correlation on the magnitude of the relative Eisenbud-Wigner-Smith (EWS) timedelay in the photoionization process into two different ionic channels. One channel, the ground state channel in the ion, is accessible without electron correlation. The other channel is only accessible when including electron correlation. For theory beyond the mean-field time-dependent HartreeFock, the EWS time-delay for the photon energy analyzed is quite insensitive to the considered active orbital spaces.

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Section: Introductionmentioning

confidence: 99%

Electron correlation in beryllium: Effects in the ground state, short-pulse photoionization, and time-delay studies

Omiste

Madsen

2017

Phys. Rev. A

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“…[4][5][6][7]) dynamics on the atomic time-and length scales. It is sensitive to various aspects of electronic dynamics, from attosecond processes in neutral systems [8,9] to hole dynamics in ions [4][5][6][7], correlation-driven channel interaction [10][11][12], and time-and space-resolved information on electronic transitions from different molecular orbitals [13][14][15].…”

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confidence: 99%

Effect of multiple conduction bands on high-harmonic emission from dielectrics

2015

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We find that, for sufficiently strong mid-IR fields, transitions between different conduction bands play an important role in the generation of high-order harmonics in a dielectric. The transitions make a significant contribution to the harmonic signal, and they can create a single effective band for the motion of an electron wave packet. We show how high harmonic spectra produced during the interaction of ultrashort laser pulses with periodic solids provide a spectroscopic tool for understanding the effective band structure that controls electron dynamics in these media.PACS numbers: 42.50. Hz, 42.65.Ky, High-order harmonic generation (HHG) from gas targets is now used as a spectroscopic tool for imaging nuclear (see e.g. [1][2][3]) and electronic (see e.g. [4][5][6][7]) dynamics on the atomic time-and length scales. It is sensitive to various aspects of electronic dynamics, from attosecond processes in neutral systems [8,9] to hole dynamics in ions [4][5][6][7], correlation-driven channel interaction [10][11][12], and time-and space-resolved information on electronic transitions from different molecular orbitals [13][14][15].We show that HHG spectra from periodic solids give insight into the effective band structure established by a strong driving mid-infrared laser field. Pioneering experiments on high harmonic generation from dielectrics [16,17] stimulated a simple model offering semi-classical insight into the underlying physics. In this model ([16, 18]; see also [19]) electrons first tunnel from a valence band (VB) to a conduction band (CB) at the maxima of the electric field. There, they are driven along the single conduction band by the field. The harmonic intensity at frequency ω is then given by |ωJ(ω)| 2 , where J(ω) is the Fourier transform of the current, j(t), in the conduction band, ε(k). Since in this model j(t) ∝ v(t) ∝ dε/dk, where v(t) is the electron group velocity, analysis of the harmonic spectrum can yield information about the band structure (dε/dk). This picture predicts that, when the driving mid-IR laser is sufficiently strong to rapidly accelerate electrons to the edge of the Brillouin zone (BZ), Bragg reflections (Bloch oscillations) within the single band would generate most of the high harmonics.However, if electrons quickly move past the gap between adjacent CBs, they may undergo an interband transition. In this case, the harmonic signal also comes from coherences between all participating bands, including the VB [17,20]. Additionally it is also important to account for the temporal structure of all interband transitions, including the VB to CB transition, see e.g. [21]. Recent theoretical analysis of HHG in bulk solids by Vampa et al. [22] and Higuchi et al. [23] accounted for the temporal structure of interband excitations, but as two-band models were used in both cases, transitions between conduction bands were not considered.We show that the inclusion of multiple conduction bands leads to additional contributions to the highharmonic signal and that, in spite of the increasin...

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“…The task is to define the function (p C A(t)) for a realistic system and include long-range and polarization [55] effects. For example, one can use the results of [54], where the ionization amplitude is represented as:…”

Section: Discussionmentioning

confidence: 99%

“…Alternatively, one can use the R-matrix approach (see [60,61]). Both allow one to incorporate the full complexity of the recombination process, including the channel coupling due to the electron-electron correlation and automatically include the exchange effects in recombination [55,62,63]. The drawback of these methods, at the moment, is the absence of the laser field in the calculations of the recombination amplitudes.…”

Section: Discussionmentioning

confidence: 99%

Multielectron High Harmonic Generation: Simple Man on a Complex Plane

Smirnova

Ivanov

2014

Attosecond and XUV Physics

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IntroductionAttosecond science has emerged with the discovery of coherent electron-ion collisions induced by a strong laser field, usually referred to as "recollisions" [1]. This discovery was initiated by the numerical experiments of K. Schafer, J. Krause and K. Kulander (see [2]). The work [1] drew on the concepts developed by F. Brunel and colleagues [3][4][5]. It has also been predated by the concept of the "atomic antenna" [6] developed by M. Kuchiev. With the benefit of hindsight, we now see the "atomic antenna" [6] as the earliest quantum counterpart of the classical picture developed by [1,7]. 1)The classical picture of strong-field-induced ionization dynamics is summarized as follows. Once ionization removes an electron from an atom or a molecule, this electron finds itself in the strong oscillating laser field. Newton's equations of motion show that, within one or a few cycles after ionization, the oscillating electron can be driven back by the laser field to reencounter the parent ion. During this reencounter, referred to as recollision, the electron can do many things: scatter elastically (diffract), scatter inelastically (excitation or ionization of the parent ion), or radiatively recombine with the ion. It is this latter process that we will focus on here. The classical picture is usually referred to as the three-step model, or the simple man model. 2) 1) While the quantum vision of [6] has predated the classical picture, at that time it lacked the striking clarity and transparency of the classical model [1], which linked several key -and seemingly disparate -strong-field phenomena, like high harmonic generation, production of very high-energy electrons, and extreme efficiency of double ionization. The history of this discovery and of its impact on nonlinear optics and technology are rich and interesting in their own right. Some of it is recounted, from a more historical perspective, in Chapter 10. Our purpose here is different -we simply urge the reader to read the papers [3-6, 8], as well as a seemingly unrelated paper [9]. 2) As far as one of us (M.I.) can remember, the latter term has been used by K. Kulander, K. Schafer and H.-G. Muller, who have largely contributed to the development of this classical model. Attosecond and XUV Physics, First Edition. Edited by Thomas Schultz and Marc Vrakking.

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Exchange and polarization effect in high-order harmonic imaging of molecular structures

Cited by 45 publications

References 86 publications

Electron correlation in beryllium: Effects in the ground state, short-pulse photoionization, and time-delay studies

Electron correlation in beryllium: Effects in the ground state, short-pulse photoionization, and time-delay studies

Effect of multiple conduction bands on high-harmonic emission from dielectrics

Multielectron High Harmonic Generation: Simple Man on a Complex Plane

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