Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Study of laser-driven multielectron dynamics of Ne atom using
  time-dependent optimized second-order many-body perturbation theory   We calculate the high-harmonic generation (HHG) spectra, strong-field
ionization, and time-dependent dipole-moment of Ne using explicitly
time-dependent optimized second-order many-body perturbation method (TD-OMP2)
where both orbitals and amplitudes are time-dependent. We consider
near-infrared (800 nm) and mid-infrared (1200 nm) laser pulses with very high
intensities ($5\times10^{14}$, $8\times10^{14}$ , and $1\times10^{15}$
W/cm$^2$), required for strong-field experiments with the high-ionization
potential (21.6 eV) atom. We compare the result of the TD-OMP2 method with the
time-dependent complete-active-space self-consistent field method and the
time-dependent Hartree-Fock method. Further, we report the implementation of
the TD-CC2 method within the chosen active space, which is also a second-order
approximation to the TD-CCSD method, and present results of time-dependent
dipole-moment and HHG spectra with an intensity of $5\times10^{13}$ W/cm$^2$ at
a wavelength of 800 nm. It is found that the TD-CC2 method is not stable in the
case with a higher laser intensity, and it does not provide a gauge-invariant
description of the physical properties, which makes TD-OMP2 a superior choice
to reach out to larger chemical systems, especially for the study of
strong-field dynamics. The obtained results indicate that the TD-OMP2 method
shows moderate performance, overestimating the response of Ne, while TDHF
underestimates it. Nevertheless, it is remarkable that stable computation of
such highly nonlinear nonperturbative phenomena is possible within the
framework of time-dependent perturbation method, by virtue of the
nonperturbative inclusion of the laser-electron interaction and time-dependent
optimization of orbitals.

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The categories of this paper are: cond-mat
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The categories of this paper are: gr-qc
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The categories of this paper are: hep-lat
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The categories of this paper are: supr-con
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The categories of this paper are: ao-sci
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The categories of this paper are: adap-org
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The categories of this paper are: mtrl-th
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The categories of this paper are: solv-int
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The categories of this paper are: bayes-an
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The categories of this paper are: quant-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: comp-gas
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The categories of this paper are: hep-ex
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The categories of this paper are: nucl-th
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The categories of this paper are: acc-phys
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The categories of this paper are: chem-ph