Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Classical collisional trajectories as the source of strong-field double
  ionization of helium in the knee regime   In this paper, a quasistatic model is extended to describe the double
ionization of Helium in intense linearly polarized field, yielding achieve an
insight to the two-electron correlation effect in the ionization dynamics. Our
numerical calculations reproduce the excessive double ionization and the
photoelectron spectra observed experimentally both quantitatively and
qualitatively. Moreover, it is shown that the classical collisional
trajectories are the main source of the double ionization in the knee regime
and responsible for the unusual angular distribution of the photoelectrons.

17
The categories of this paper are: q-fin
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The categories of this paper are: solv-int
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The categories of this paper are: math-ph
18
The categories of this paper are: econ
27
The categories of this paper are: comp-gas
0
The categories of this paper are: hep-ph
31
The categories of this paper are: ao-sci
32
The categories of this paper are: atom-ph
37
The categories of this paper are: supr-con
28
The categories of this paper are: alg-geom
25
The categories of this paper are: patt-sol
33
The categories of this paper are: plasm-ph
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The categories of this paper are: eess
12
The categories of this paper are: nucl-th
5
The categories of this paper are: gr-qc
24
The categories of this paper are: dg-ga