Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Carbon chain anions and the growth of complex organic molecules in
  Titan's ionosphere   Cassini discovered a plethora of neutral and ionised molecules in Titan's
ionosphere including, surprisingly, anions and negatively charged molecules
extending up to 13,800 u/q. In this letter we forward model the Cassini
electron spectrometer response function to this unexpected ionospheric
component to achieve an increased mass resolving capability for negatively
charged species observed at Titan altitudes of 950-1300 km. We report on
detections consistently centered between 25.8-26.0 u/q and between 49.0-50.1
u/q which are identified as belonging to the carbon chain anions,
CN$^-$/C$_3$N$^-$ and/or C$_2$H$^-$/C$_4$H$^-$, in agreement with chemical
model predictions. At higher ionospheric altitudes, detections at 73-74 u/q
could be attributed to the further carbon chain anions C$_5$N$^-$/C$_6$H$^-$
but at lower altitudes and during further encounters, extend over a higher
mass/charge range. This, as well as further intermediary anions detected at
$>$100 u, provide the first evidence for efficient anion chemistry in space
involving structures other than linear chains. Furthermore, at altitudes below
$\sim$1100 km, the low mass anions ($<$150 u/q) were found to deplete at a rate
proportional to the growth of the larger molecules, a correlation that
indicates the anions are tightly coupled to the growth process. This study adds
Titan to an increasing list of astrophysical environments where chain anions
have been observed and shows that anion chemistry plays a role in the formation
of complex organics within a planetary atmosphere as well as in the
interstellar medium.

29
The categories of this paper are: funct-an
24
The categories of this paper are: dg-ga
10
The categories of this paper are: q-bio
31
The categories of this paper are: ao-sci
19
The categories of this paper are: eess
13
The categories of this paper are: quant-ph
18
The categories of this paper are: econ
28
The categories of this paper are: alg-geom
0
The categories of this paper are: hep-ph
27
The categories of this paper are: comp-gas
30
The categories of this paper are: q-alg
21
The categories of this paper are: adap-org
5
The categories of this paper are: gr-qc
11
The categories of this paper are: hep-lat
12
The categories of this paper are: nucl-th
2
The categories of this paper are: math