Harmonic generation by noble-gas atoms in the near-IR regime using<i>ab initio</i>time-dependent<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>R</mml:mi></mml:math>-matrix theory

Hassouneh, Ola; Brown, A. C.; Hart, H. W. van der

doi:10.1103/physreva.90.043418

Cited by 32 publications

(35 citation statements)

References 27 publications

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“…6. This compares favourably both with the experiment [3] (green line) and against an analogous R-matrix calculation [16] (blue dashed line). This is in particularly true for the location of the spectral cut-off albeit the relative magnitude of the experiment is marginally higher.…”

Section: B Single Colorsupporting

confidence: 69%

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Correlation enhancement of high-order harmonic generation in Xe

et al. 2019

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We consider the process of high-order harmonics generation (HHG) in the xenon atom enhanced by the inter-shell correlation between the valence 5p and inner 4d shells. We derive the HHG spectrum from a numerical solution of the one-electron time-dependent Schrödinger equation multiplied by the enhancement factor taken as the photoionization cross-sections ratio calculated with and without the inter-shell correlation. Such a simplified approach is adequate to describe the experimental HHG spectrum reported by Shiner et al. [Nat. Phys. 7, 464 (2011)] generated by a single color IR laser. Similarly, we find good agreement when applied to the two-color driven HHG spectra reported by Faccialá et al. [Phys. Rev. Lett. 117, 093902 (2016)].

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Section: B Single Colorsupporting

confidence: 69%

“…The comparison proved very convincing. Subsequent, more refined, theoretical treatment within the strong-field approximation [15] and the timedependent R-matrix theory [16,17] confirmed this analysis.…”

Section: Introductionmentioning

confidence: 70%

Correlation enhancement of high-order harmonic generation in Xe

et al. 2019

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“…Importantly, these distinct numerical approaches benefit from rather natural modes of parallelization, which in RMT are combined in an efficient and scalable implementation to address the key computational difficulties of modelling strong-field dynamics. The RMT method has been applied to many cutting-edge problems in strong-field physics, including the experimentally relevant techniques of HHG [21][22][23][24], ATAS [25] and strong-field rescattering [26].…”

Section: Introductionmentioning

confidence: 99%

RMT: R-matrix with time-dependence. Solving the semi-relativistic, time-dependent Schrödinger equation for general, multielectron atoms and molecules in intense, ultrashort, arbitrarily polarized laser pulses

Brown

Armstrong

Benda

et al. 2020

Computer Physics Communications

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RMT is a program which solves the time-dependent Schrödinger equation for general, multielectron atoms, ions and molecules interacting with laser light. As such it can be used to model ionization (single-photon, multiphoton and strong-field), recollision (high-harmonic generation, strong-field rescattering), and more generally absorption or scattering processes with a full account of the multielectron correlation effects in a time-dependent manner. Calculations can be performed for targets interacting with ultrashort, intense laser pulses of long-wavelength and arbitrary polarization. Calculations for atoms can optionally include the Breit-Pauli correction terms for the description of relativistic (in particular, spin-orbit) effects. PROGRAM SUMMARYProgram Title: (RMT) R-matrix with time-dependence Licensing provisions: GPLv3 Programming language: Fortran Program repository available at: https://gitlab.com/UK-AMOR/RMT Computers on which the program has been tested: Cray XC40 BESKOW, Cray XC30 ARCHER, Cray XK7 TITAN, TACC Stampede2, DELL linux cluster, DELL PC Number of processors used: Min. 2, Max. tested 16,416 Number of lines in program: 25,247 Distribution format: git repository Nature of problem:The interaction of laser light with matter can be modelled with the time-dependent Schrödinger equation (TDSE). The solution of the TDSE for general, multielectron atomic and molecular systems is computationally demanding, and has previously been limited to either particular laser wavelengths and intensities, or to simple, few-electron cases. RMT overcomes this limitation by using a general approach to modelling dynamics in atoms and molecules which is applicable to multi-electron systems and a wide range of perturbative and non-perturbative phenomena. Solution method:We use the R-matrix paradigm, partitioning the interaction region into an 'inner' and an 'outer' region. In the inner region (within some small radius of the nucleus/nuclei), full account is taken of all multielectron interactions including electron exchange and correlation. In the outer region, far from the nucleus/nuclei, these are neglected and a single, ionized electron moves in the long-range potential of the residual ionic system and the laser field. The key computational aspect of the RMT approach is the use of a different numerical approach in each region, facilitating efficient parallelization without sacrificing accuracy. Given an initial wavefunction and the electric field of the driving laser pulse, the wavefunction for all subsequent times and the associated observables are computed using an explicit, Arnoldi propagator method. Additional comments including restrictions and unusual features:The description of the atomic/molecular structure is provided from other, timeindependent R-matrix codes [1][2][3], and the capabilities (in terms of structure) are, in some sense, inherited therefrom. Thus, the atomic calculations can optionally include Breit-Pauli relativistic corrections to the Hamiltonian, in order to account

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“…The RMT method has already been applied to other strong field phenomena, including high-harmonic generation [27], but the accurate and efficient determination of the multielectron wave function over such a large region of space is a first for calculations of this type. Indeed, the present calculation of ATD in negative ions provides an extremely sensitive test of the wave function accuracy.…”

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confidence: 99%

Electron rescattering in strong-field photodetachment ofF−

et al. 2015

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We present ab initio studies of photoelectron spectra for above threshold detachment (ATD) of F − anions in short, 1300 nm and 1800 nm laser pulses. We identify and assess the importance of electron rescattering in strong-field photodetachment of a negative ion through comparison with an analytic, Keldysh-type approach, demonstrating the capability of ab-initio computation in the challenging near-IR regime. We further assess the influence of the strong electron correlation on the photodetachment.PACS numbers: 32.80.Gc 31.15.VElectron rescattering is one of the fundamental processes occuring in the interaction between matter and intense light fields [1]. The mechanism is a critical part of the well known three-step or recollision model for high harmonic generation (HHG) or strong field double ionisation. According to the model an electron is first ionised, then driven by a strong laser field, before recolliding with the parent ion, either recombining, leading to HHG [2,3], or rescattering, leading to high-energy electron emission [4,5], or non-sequential double ionisation [6].Electron rescattering also encodes structural information about the residual ion into the wavepacket of the ejected electron and can thus be exploited as an experimental probe of the structure of the parent ion [1]. The technique is especially sensitive as the current density of a recolliding electron wavepacket exceeds that of conventional electron sources by several orders of magnitude [7]. Furthermore, the inherently subcycle and phase-locked nature of the recollision process gives access to electron dynamics on the attosecond scale, via information embedded in the photoelectron spectrum [8,9].One of the open questions in strong-field science concerns the importance of electron rescattering for negative ions. Significant progress has been made in understanding and controlling the equivalent process in neutral atoms and positive ions [10], but above-threshold detachment (ATD) presents a different challenge. The small binding energy allows detachment at low intensities. Hence to reach significant recollision energies, nearinfrared (NIR) laser fields are required. In addition, the absence of the Coulomb potential makes it easier for the electron wavepacket to spread out, reducing the effect of rescattering [4,5]. While evidence for rescattering from negative ions has been found experimentally [11], no verification has yet been provided from ab initio theory. A theoretical approach, based on first order correction to the strong field approximation, was able to reproduce experimental results from Br − and F − , [12] but a more recent study, using a numerical solution of the time-dependent Schrödinger equation (TDSE), found "no qualitative evidence of rescattering" for H − [13]. In this report we demonstrate that ab-initio theory can be used to investigate rescattering in the NIR regime.An additional complication in the description of negative ions is the much larger influence of dielectronicrepulsion. Several approximate methods have been empl...

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Harmonic generation by noble-gas atoms in the near-IR regime usingab initiotime-dependentR-matrix theory

Cited by 32 publications

References 27 publications

Correlation enhancement of high-order harmonic generation in Xe

Correlation enhancement of high-order harmonic generation in Xe

RMT: R-matrix with time-dependence. Solving the semi-relativistic, time-dependent Schrödinger equation for general, multielectron atoms and molecules in intense, ultrashort, arbitrarily polarized laser pulses

Electron rescattering in strong-field photodetachment ofF−

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