Hybrid Gaussian–discrete-variable representation for one- and two-active-electron continuum calculations in molecules

Yip, Frank L.; McCurdy, C. William; Rescigno, T. N.

doi:10.1103/physreva.90.063421

Cited by 24 publications

(20 citation statements)

References 29 publications

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“…To overcome this problem for diatomic molecules, we use two-center prolate spheroidal coordinates, in the following. Alternatively, also for larger molecules with more complicated geometries, a combined Gaussian and discrete variable representation (DVR) can be applied [62][63][64].…”

Section: B Single-particle Basismentioning

confidence: 99%

Correlation effects in strong-field ionization of heteronuclear diatomic molecules

et al. 2016

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We develop a time-dependent theory to investigate electron dynamics and photoionization processes of diatomic molecules interacting with strong laser fields including electron-electron correlation effects. We combine the recently formulated time-dependent generalized-active-space configuration interaction theory [D. Hochstuhl and M. Bonitz, Phys. Rev. A 86, 053424 (2012); S. Bauch et al., Phys. Rev. A 90, 062508 (2014)] with a prolate spheroidal basis set including localized orbitals and continuum states to describe the bound electrons and the outgoing photoelectron. As an example, we study the strong-field ionization of the two-center four-electron lithium hydride molecule in different intensity regimes. By using single-cycle pulses, two orientations of the asymmetric heteronuclear molecule are investigated: Li−H, with the electrical field pointing from H to Li, and the opposite case of H−Li. The preferred orientation for ionization is determined and we find a transition from H−Li, for low intensity, to Li−H, for high intensity. The influence of electron correlations is studied at different levels of approximation, and we find a significant change in the preferred orientation. For certain intensity regimes, even an interchange of the preferred configuration is observed, relative to the uncorrelated simulations. Further insight is provided by detailed comparisons of photoelectron angular distributions with and without correlation effects taken into account.

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Section: B Single-particle Basismentioning

confidence: 99%

Correlation effects in strong-field ionization of heteronuclear diatomic molecules

et al. 2016

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“…Faure et al [31] extended the work of Nestmann and Peyerimhoff to the possibility of fitting a linear combination of GTO basis functions to a set of Coulomb continuum functions (i.e., the continuum eigenfunctions obtained in presence of the Coulomb potential −Z/|r|, with Z the nuclear charge). Finally, some hybrid methods have also been proposed, combining Gaussian functions with finiteelement/discrete-variable representation techniques [32] or with B-spline basis sets [33]. Note that an alternative approach to Gaussian basis sets is given by the use of Sturmian functions [34,35].…”

Section: Introductionmentioning

confidence: 99%

Gaussian continuum basis functions for calculating high-harmonic generation spectra

Coccia

Mussard

Labeye

et al. 2016

Int. J. Quantum Chem.

104

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We explore the computation of high-harmonic generation spectra by means of Gaussian basis sets in approaches propagating the time-dependent Schrödinger equation. We investigate the efficiency of Gaussian functions specifically designed for the description of the continuum proposed by Kaufmann et al. [J. Phys. B 22, 2223(1989]. We assess the range of applicability of this approach by studying the hydrogen atom, i.e. the simplest atom for which "exact" calculations on a grid can be performed. We notably study the effect of increasing the basis set cardinal number, the number of diffuse basis functions, and the number of Gaussian pseudo-continuum basis functions for various laser parameters. Our results show that the latter significantly improve the description of the low-lying continuum states, and provide a satisfactory agreement with grid calculations for laser wavelengths λ0 = 800 and 1064 nm. The Kaufmann continuum functions therefore appear as a promising way of constructing Gaussian basis sets for studying molecular electron dynamics in strong laser fields using time-dependent quantum-chemistry approaches.

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“…Thus most solutions proposed in the literature have adopted a more pragmatical approach, which is to combine existing QCPs with scattering methods that incorporate the latter basis functions. For instance, recently proposed methods complement the short-range part represented by Gaussian functions with a finite element (FE) representation of the radial coordinate [40,41], or a discrete variable representation (DVR) [42][43][44][45][46], or even plane waves [47]. Others just get rid of all exponentially decreasing functions by fitting them to a multicenter B-spline expansion and adding additional B-splines for the continuum part [48].…”

Section: Introductionmentioning

confidence: 99%

Photoionization using the xchem approach: Total and partial cross sections of Ne and resonance parameters above the 2s22p5 threshold

et al. 2017

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The XCHEM approach interfaces well established quantum chemistry packages with scattering numerical methods in order to describe single-ionization processes in atoms and molecules. This should allow one to describe electron correlation in the continuum at the same level of accuracy as quantum chemistry methods do for bound states. Here we have applied this method to study multichannel photoionization of Ne in the vicinity of the autoionizing states lying between the 2s 2 2p 5 and 2s2p 6 ionization thresholds. The calculated total photoionization cross sections are in very good agreement with the absolute measurement of Samson et al.[J. Electron Spectrosc. Relat. Phenom. 123, 265 (2002)], and with independent benchmark calculations performed at the same level of theory. From these cross sections, we have extracted resonance positions, total autoionization widths, Fano profile parameters, and correlation parameters for the lowest three autoionizing states. The values of these parameters are in good agreement with those reported in earlier theoretical and experimental work. We have also evaluated β asymmetry parameter and partial photoionization cross sections and, from the latter, partial autoionization widths and Starace parameters for the same resonances, not yet available in the literature. Resonant features in the calculated β parameter are in good agreement with the experimental observations. We have found that the three lowest resonances preferentially decay into the 2p −1 d continuum rather than into the 2p −1 s one [Phys. Rev. A 89, 043415 (2014)], in agreement with previous expectations, and that in the vicinity of the resonances the partial 2p −1 s cross section can be larger than the 2p −1 d one, in contrast with the accepted idea that the latter should amply dominate in the whole energy range. These results show the potential of the XCHEM approach to describe highly correlated process in the ionization continuum of many-electron systems, in particular molecules, for which the XCHEM code has been specifically designed.

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Hybrid Gaussian–discrete-variable representation for one- and two-active-electron continuum calculations in molecules

Cited by 24 publications

References 29 publications

Correlation effects in strong-field ionization of heteronuclear diatomic molecules

Correlation effects in strong-field ionization of heteronuclear diatomic molecules

Gaussian continuum basis functions for calculating high-harmonic generation spectra

Photoionization using the xchem approach: Total and partial cross sections of Ne and resonance parameters above the 2s22p5 threshold

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