Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The temporal changes in the emission spectrum of Comet 9P/Tempel 1 after
  Deep Impact   The time dependence of the changes in the emission spectra of Comet 9P/Tempel
1 after Deep Impact are derived and discussed. This was a unique event because
for the first time it gave astronomers the opportunity to follow the time
history of the formation and decay of O(1S), OH, CN, C2, C3, NH, and NH2. Least
squares fits of a modified Haser model with constraints using known rate
constants were fit to the observed data. In the case of OH a simple two-step
Haser model provides a reasonable fit to the observations. Fitting the
emissions from O(1S), CN, C2, C3, NH, and NH2 requires the addition of a
delayed component to a regular two or three step Haser model. From this
information a picture of the Deep Impact encounter emerges where there is an
initial formation of gas and dust, which is responsible for the prompt emission
that occurs right after impact. A secondary source of gas starts later after
impact when the initial dust has dissipated enough so that solar radiation can
reach the surface of freshly exposed material. The implications of this and
other results are discussed in terms of the implications on the structure and
composition of the comet's nucleus.

7
The categories of this paper are: hep-th
36
The categories of this paper are: cmp-lg
15
The categories of this paper are: nucl-ex
22
The categories of this paper are: chao-dyn
5
The categories of this paper are: gr-qc
10
The categories of this paper are: q-bio
9
The categories of this paper are: nlin
35
The categories of this paper are: mtrl-th
2
The categories of this paper are: math
19
The categories of this paper are: eess
32
The categories of this paper are: atom-ph
25
The categories of this paper are: patt-sol
30
The categories of this paper are: q-alg
34
The categories of this paper are: chem-ph
18
The categories of this paper are: econ
20
The categories of this paper are: acc-phys