Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the band-to-continuum intensity ratio in the infrared spectra of
  interstellar carbonaceous dust   Published interpretations of the relative intensity variations of the
Unidentified Infrared Bands (UIBs) and their underlying continuum are
discussed. An alternative model is proposed, in which a single carrier for both
emits a) mostly a continuum when it is electronically excited by photons
(visible or UV), or b) exclusively the UIBs, when only chemical energy is
deposited by H capture on its surface, inducing only nuclear vibrations. The
bands will dominate in atomic H regions but will be overcome by thermal
continuum radiation when the ambient field is strong but lacks dissociating
photons (900-1100 Angstroms). The model applies to PDRs as well as to limbs of
molecular clouds in the ISM and agrees quantitatively with recent satellite
observations. It gives indications on atomic H density and UIB intensity
provided the ambient radiation field is known. It invokes no chemical,
electronic, structural or size change in order to interpret the observed
intensity variations.

19
The categories of this paper are: eess
18
The categories of this paper are: econ
16
The categories of this paper are: stat
3
The categories of this paper are: physics
12
The categories of this paper are: nucl-th
5
The categories of this paper are: gr-qc
34
The categories of this paper are: chem-ph
0
The categories of this paper are: hep-ph
20
The categories of this paper are: acc-phys
37
The categories of this paper are: supr-con
4
The categories of this paper are: cond-mat
15
The categories of this paper are: nucl-ex
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The categories of this paper are: solv-int
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The categories of this paper are: dg-ga
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The categories of this paper are: comp-gas
11
The categories of this paper are: hep-lat