Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Accurate photoionisation cross section for He at non-resonant photon
  energies   The total single-photon ionisation cross section was calculated for helium
atoms in their ground state. Using a full configuration-interaction approach
the photoionisation cross section was extracted from the complex-scaled
resolvent. In the energy range from ionisation threshold to 59\,eV our results
agree with an earlier $B$-spline based calculation in which the continuum is
box discretised within a relative error of $0.01\%$ in the non-resonant part of
the spectrum. Above the $\He^{++}$ threshold our results agree on the other
hand very well to a recent Floquet calculation. Thus our calculation confirms
the previously reported deviations from the experimental reference data outside
the claimed error estimate. In order to extend the calculated spectrum to very
high energies, an analytical hydrogenic-type model tail is introduced that
should become asymptotically exact for infinite photon energies. Its
universality is investigated considering also H$^-$, Li$^+$, and HeH$^+$. With
the aid of the tail corrections to the dipole approximation are estimated.

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The categories of this paper are: astro-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: bayes-an
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The categories of this paper are: ao-sci
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The categories of this paper are: stat
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The categories of this paper are: hep-th
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The categories of this paper are: chao-dyn
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The categories of this paper are: nucl-th
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The categories of this paper are: econ
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The categories of this paper are: q-fin
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The categories of this paper are: alg-geom
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The categories of this paper are: gr-qc
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The categories of this paper are: patt-sol
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The categories of this paper are: math-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: dg-ga