Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Photoelectron distribution of non-resonant two-photon ionization of
  neutral atoms   Photoelectron angular distributions following the non-resonant two-photon
K-shell ionization of neutral atoms are studied theoretically. Using the
independent particle approximation and relativistic second-order perturbation
theory, the contributions of screening and relativistic effects to the
photoelectron angular distribution are evaluated. A simple nonrelativistic
expression is presented for the angle-differential cross section in dipole
approximation for two-photon ionization by elliptically polarized photons, and
its limitations are analyzed numerically. Moreover, we show that screening
effects of the inactive electrons can significantly affect the photoelectron
distributions and can also lead to a strong elliptical dichroism. Numerical
results are resented for the case of two-photon K-shell ionization of neutral
Ne, Ge, Xe, and U atoms.

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The categories of this paper are: math
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The categories of this paper are: math-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: dg-ga
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The categories of this paper are: q-fin
31
The categories of this paper are: ao-sci
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The categories of this paper are: stat
18
The categories of this paper are: econ
5
The categories of this paper are: gr-qc
22
The categories of this paper are: chao-dyn
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The categories of this paper are: solv-int
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The categories of this paper are: eess
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The categories of this paper are: nucl-ex
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The categories of this paper are: chem-ph
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The categories of this paper are: alg-geom
33
The categories of this paper are: plasm-ph