Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the visible continuum and bands in the interstellar extinction curve
  II   Any distortion of a chemical structure causes new features to appear in the
absorption spectrum of the structure, especially in the visible and near UV
(see Paper I). Chemical modeling, using molecular orbital theory, showed that
the continuum resulting from the accumulation of weak new bands in that range,
correctly mimics the continuum measured in the laboratory on pure synthesized
silicates, in the transparency spectral range, as well as in the InterStellar
extinction curve in the same range.
  The present paper explores in more detail the strong discrete bands that
emerge from the continuum due to distortion. It is found that different types
of structure (linear or compact, carbon- or silicon-bearing) have each a
limited number of strong, characteristic, bands at different wavelengths.
  Distortion is only one instance of ``defects'' that enrich the vis/UV
absorption spectrum; others are: vacancies and voids, substitutions, inclusions
in interstices, impurities, dangling bonds. The accumulation of these result in
an ``amorphous'' structural state. Several examples of known amorphous
materials, both carbon- and silicon-bearing, that have been analyzed in the
laboratory, and simulated theoretically, are described below, thus extending
the scope of this work. A final section lists several fields of astrophysics
that have used, or may use, amorphous models of dust.

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The categories of this paper are: comp-gas
16
The categories of this paper are: stat
29
The categories of this paper are: funct-an
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The categories of this paper are: mtrl-th
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The categories of this paper are: solv-int
13
The categories of this paper are: quant-ph
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The categories of this paper are: dg-ga
2
The categories of this paper are: math
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The categories of this paper are: econ
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-ex
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The categories of this paper are: q-alg
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-lat
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The categories of this paper are: ao-sci
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The categories of this paper are: chem-ph