Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The changing rotational excitation of C_3 in comet 9P/Tempel 1 during
  Deep Impact   The 4050\AA\ band of C$_3$ was observed with Keck/HIRES echelle spectrometer
during the {\em Deep Impact} encounter. We perform a 2-dimensional analysis of
the exposures in order to study the spatial, spectral, and temporal changes in
the emission spectrum of C$_3$. The rotational population distribution changes
after impact, beginning with an excitation temperature of $\sim$45\,K at impact
and increasing for 2\,hr up to a maximum of 61$\pm$5\,K. From 2 to 4 hours
after impact, the excitation temperature decreases to the pre-impact value. We
measured the quiescent production rate of C$_3$ before the encounter to be 1.0
$\times 10^{23}$ s$^{-1}$, while 2 hours after impact we recorded a peak
production rate of 1.7 $\times 10^{23}$ s$^{-1}$. Whereas the excitation
temperature returned to the pre-impact value during the observations, the
production rate remained elevated, decreasing slowly, until the end of the
4\,hr observations. These results are interpreted in terms of changing gas
densities in the coma and short-term changes in the primary chemical production
mechanism for C$_{3}$.

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The categories of this paper are: physics
20
The categories of this paper are: acc-phys
33
The categories of this paper are: plasm-ph
14
The categories of this paper are: math-ph
23
The categories of this paper are: solv-int
0
The categories of this paper are: hep-ph
5
The categories of this paper are: gr-qc
25
The categories of this paper are: patt-sol
26
The categories of this paper are: bayes-an
18
The categories of this paper are: econ
37
The categories of this paper are: supr-con
11
The categories of this paper are: hep-lat
32
The categories of this paper are: atom-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: nucl-th
31
The categories of this paper are: ao-sci