Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Angular distributions of secondary electrons in fast particle-atom
  scattering   We present the angular distribution of electrons knocked out from an atom in
a fast charge particle collision at small momentum transfer. It is determined
not only by dipole but also by quadrupole transitions, the contribution of
which can be considerably enhanced as compared to the case of photoionization.
There the non-dipole parameters are suppressed as compared to the dipole ones
by the parameter \omega R/c << 1, where is the photon energy, R is the ionized
shell radius and c is the speed of light. This suppression in fast
electron-atom collisions can be considerably reduced: the corresponding
expansion parameter \omega R/ \nu << 1 is much bigger than in photoionization,
since the speed of the incoming electron is much smaller than c. In formation
of the angular distribution it is decisively important that the ionizing field
in collision process is longitudinal, while in photoionization - it is
transversal.
  We illustrate the general formulas by concrete results for outer s-, p-, and
some nd-subshells of multi-electron noble gas atoms Ar, Kr and Xe, at several
transferred momentum values: q=0.0, 0.1, 1.1, 2.1. Even for very small
transferred momentum q, i.e. in the so-called optical limit, the deviations
from the photoionization case are prominent.

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The categories of this paper are: nucl-th
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The categories of this paper are: hep-th
37
The categories of this paper are: supr-con
0
The categories of this paper are: hep-ph
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The categories of this paper are: cs
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The categories of this paper are: math-ph
22
The categories of this paper are: chao-dyn
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The categories of this paper are: econ
30
The categories of this paper are: q-alg
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The categories of this paper are: cmp-lg
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The categories of this paper are: bayes-an
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The categories of this paper are: patt-sol
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The categories of this paper are: solv-int
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The categories of this paper are: q-fin
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The categories of this paper are: cond-mat
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The categories of this paper are: alg-geom