Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Complex Chemistry in Star-Forming Regions: An Expanded Gas-Grain Warm-up
  Chemical Model   Gas-phase processes were long thought to be the key formation mechanisms for
complex organic molecules in star-forming regions. However, recent experimental
and theoretical evidence has cast doubt on the efficiency of such processes.
Grain-surface chemistry is frequently invoked as a solution, but until now
there have been no quantitative models taking into account both the high degree
of chemical complexity and the evolving physical conditions of star-forming
regions. Here, we introduce a new gas-grain chemical network, wherein a wide
array of complex species may be formed by reactions involving radicals. The
radicals we consider (H, OH, CO, HCO, CH3, CH3O, CH2OH, NH and NH2) are
produced primarily by cosmic ray-induced photodissociation of the granular ices
formed during the colder, earlier stages of evolution. The gradual warm-up of
the hot core is crucial to the formation of complex molecules, allowing the
more strongly-bound radicals to become mobile on grain surfaces. This type of
chemistry is capable of reproducing the high degree of complexity seen in Sgr
B2(N), and can explain the observed abundances and temperatures of a variety of
previously detected complex organic molecules, including structural isomers.
Many other complex species are predicted by this model, and several of these
species may be detectable in hot cores. Differences in the chemistry of high-
and low-mass star-formation are also addressed; greater chemical complexity is
expected where evolution timescales are longer.

27
The categories of this paper are: comp-gas
13
The categories of this paper are: quant-ph
33
The categories of this paper are: plasm-ph
37
The categories of this paper are: supr-con
16
The categories of this paper are: stat
3
The categories of this paper are: physics
7
The categories of this paper are: hep-th
26
The categories of this paper are: bayes-an
19
The categories of this paper are: eess
35
The categories of this paper are: mtrl-th
18
The categories of this paper are: econ
0
The categories of this paper are: hep-ph
1
The categories of this paper are: cs
23
The categories of this paper are: solv-int
22
The categories of this paper are: chao-dyn
8
The categories of this paper are: hep-ex