Excited-state populations in the multiconfiguration time-dependent Hartree–Fock method

Lötstedt, Erik; Szidarovszky, Tamás; Faisal, Farhard; Katō, Takako; Yamanouchi, Kaoru

doi:10.1088/1361-6455/ab7c3b

Cited by 9 publications

(9 citation statements)

References 146 publications

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“…Here, we apply a similar method to obtain the excited initial state Ne * by restricting the symmetry of the state used for propagation in imaginary time. Note that recently, a new method was proposed to compute excited states using an extension of MCTDHF that generalizes the state-average approach of CASSCF methods [42]. Specifically, in our present case, the first excited state of Ne corresponds to the excitation of a 2p electron to the 3s shell, i. e., the main configuration of the excited state is (1s…”

Section: Resultsmentioning

confidence: 82%

Photoionization of aligned excited states in neon by attosecond laser pulses

Omiste,

Madsen

2020

Preprint

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We describe numerically the ionization process induced by linearly and circularly polarized XUV attosecond laser pulses on an aligned atomic target, specifically, the excited state Ne * (1s 2 2s 2 2p 5 [ 2 P o 1/2 ]3s[ 1 P o ]). We compute the excited atomic state by applying the time-dependent restricted-active-space self-consistent field (TD-RASSCF) method to fully account for the electronic correlation. We find that correlation-assisted ionization channels can dominate over channels accessible without correlation. We also observe that the rotation of the photoelectron momentum distribution by circularly polarized laser pulses compared to the case of linear polarization can be explained in terms of differences in accessible ionization channels. This study shows that it is essential to include electron correlation effects to obtain an accurate description of the photoelectron emission dynamics from aligned excited states.

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Section: Resultsmentioning

confidence: 82%

Photoionization of aligned excited states in neon by attosecond laser pulses

Omiste,

Madsen

2020

Preprint

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“…The equations of motion for the spin-orbitals and the CI coefficients are derived by applying the time-dependent variational principle [39,40]. The MCTDHF method has previously been applied to He in the calculation of two-photon ionization probabilities [48], high-harmonic spectra [49], above-threshold photoelectron spectra [50], and strong-field excitation probabilities [51].…”

Section: B Mctdhfmentioning

confidence: 99%

“…We solve the MCTDHF equations of motion in the same way as described in [51,55]. The details of the numerical implementation of the MCTDHF method are summarized in Appendix A.…”

Section: B Mctdhfmentioning

confidence: 99%

“…VAJVA-19-04). M. F. C. acknowledges the project Advanced research using high intensity laser produced photons and particles (CZ.02.1.01/0.0/0.0/ 16 019/0000789) from European Regional Development Fund The numerical method used for the solution of the MCTDHF equations of motion is the same as that presented in [51,55]. We describe the essential points below.…”

Section: Acknowledgmentsmentioning

confidence: 99%

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Static-field ionization model of He-like ions for diagnostics of light-field intensity

2020

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We study static-field ionization of He-like ions with nuclear charge number in the range of 2 ≤ Z ≤ 36. Both the tunneling and over-the-barrier regimes are considered. We calculate the ionization rates by three approximate methods: a fitting formula based on the Perelemov-Popov-Terent'ev (PPT) formula, a perturbative expansion in powers of 1/Z, and a single-active electron approximation, and compare them with reference ionization rates computed by the multiconfiguration time-dependent Hartree-Fock (MCTDHF) approach. The relative deviation of the rates computed by the PPT-based fitting formula and the third-order perturbation theory from the rates computed by the MCTDHF approach is found to be around 10%. We discuss quantitatively the contribution from the exchange interaction during the ionization by comparing the single-active electron rates and the reference rates in which multielectron effects are included. We find that a single-active electron approximation, where the exchange interaction is neglected, results in the overestimation of the ionization rates by 30% for He and 2% for He-like Kr, showing that the magnitude of the effect of the exchange interaction scales approximately as 1/Z.

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“…The natural approach would be to define the stationary states from the zero-field Hamiltonian and zero-field wave function using, e.g., linear response theory 47 or orthogonalityconstrained imaginary time propagation. 48 The latter approach was investigated recently within the framework of MCTDHF theory by Lötstedt et al, 49 who found that the stationarystate populations oscillate even after the pulse is turned off unless a sufficiently large number of active orbitals is included in the wave function expansion. In this work, we use both CC linear response theory 19,50,51 and equation-of-motion CC (EOMCC) theory [52][53][54][55] to propose projectors whose expectation values yield stationary-state populations.…”

Section: Introductionmentioning

confidence: 99%

Interpretation of Coupled-Cluster Many-Electron Dynamics in Terms of Stationary States

Pedersen,

Kristiansen,

Bodenstein

et al. 2020

Preprint

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We demonstrate theoretically and numerically that laser-driven many-electron dynamics, as described by bivariational time-dependent coupled-cluster theory, may be analyzed in terms of stationary-state populations. Projectors heuristically defined from linear response theory and equation-of-motion coupled-cluster theory are proposed for the calculation of stationary-state populations during interaction with laser pulses or other external forces, and conservation laws of the populations are discussed. Numerical tests of the proposed projectors, involving both linear and nonlinear optical processes for the He and Be atoms, and for the LiH, CH + , and LiF molecules, show that the laser-driven evolution of the stationary-state populations at the coupled-cluster singles-and-doubles (CCSD) level is very close to that obtained by full configurationinteraction theory provided all stationary states actively participating in the dynamics are sufficiently well approximated. When double-excited states are important for the dynamics, the quality of the CCSD results deteriorate. Observing that populations

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Excited-state populations in the multiconfiguration time-dependent Hartree–Fock method

Cited by 9 publications

References 146 publications

Photoionization of aligned excited states in neon by attosecond laser pulses

Photoionization of aligned excited states in neon by attosecond laser pulses

Static-field ionization model of He-like ions for diagnostics of light-field intensity

Interpretation of Coupled-Cluster Many-Electron Dynamics in Terms of Stationary States

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