Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Hydrogen Cyanide in Nitrogen-Rich Atmospheres of Rocky Exoplanets   Hydrogen cyanide (HCN) is a key feedstock molecule for the production of
life's building blocks. The formation of HCN in an N$_2$-rich atmospheres
requires first that the triple bond between N$\equiv$N be severed, and then
that the atomic nitrogen find a carbon atom. These two tasks can be
accomplished via photochemistry, lightning, impacts, or volcanism. The key
requirements for producing appreciable amounts of HCN are the free availability
of N$_2$ and a local carbon to oxygen ratio of C/O $\geq 1$. We discuss the
chemical mechanisms by which HCN can be formed and destroyed on rocky
exoplanets with Earth-like N$_2$ content and surface water inventories, varying
the oxidation state of the dominant carbon-containing atmospheric species. HCN
is most readily produced in an atmosphere rich in methane (CH$_4$) or acetylene
(C$_2$H$_2$), but can also be produced in significant amounts ($> 1$ ppm)
within CO-dominated atmospheres. Methane is not necessary for the production of
HCN. We show how destruction of HCN in a CO$_2$-rich atmosphere depends
critically on the poorly-constrained energetic barrier for the reaction of HCN
with atomic oxygen. We discuss the implications of our results for detecting
photochemically produced HCN, for concentrating HCN on the planet's surface,
and its importance for prebiotic chemistry.

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The categories of this paper are: hep-ph
4
The categories of this paper are: cond-mat
16
The categories of this paper are: stat
30
The categories of this paper are: q-alg
33
The categories of this paper are: plasm-ph
2
The categories of this paper are: math
18
The categories of this paper are: econ
19
The categories of this paper are: eess
17
The categories of this paper are: q-fin
11
The categories of this paper are: hep-lat
10
The categories of this paper are: q-bio
36
The categories of this paper are: cmp-lg
28
The categories of this paper are: alg-geom
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The categories of this paper are: hep-th
22
The categories of this paper are: chao-dyn
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The categories of this paper are: adap-org