Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Heterogeneous reactions between ions NH$_3$$^{+}$ and NH$^{+}$ and
  hydrocarbons adsorbed on a tungsten surface. Formation of HCN$^{+}$ in
  NH$^{+}$-surface hydrocarbons collisions   Interaction of NH$_3$$^{+}$ (ND$_3$$^{+}$) and NH$^{+}$ with a
hydrocarbon-covered tungsten surface kept at room temperature and heated to
150{\deg}C and 300{\deg}C showed a series of reactions between the projectile
ion and hydrocarbons adsorbed on the tungsten surface. Collisions with NH3+ and
particularly with ND3+ showed formation of NH$_4$$^{+}$, HCNH$^{+}$, and
CH$_2$NH$_2$$^{+}$ and ND$_3$H+, HCND$^{+}$, and CH$_2$ND$_2$$^{+}$,
respectively, with NH$_4$$^{+}$ (ND$_3$H$^{+}$) strongly prevailing at low
incident energies of the projectile ion. No formation of HCN$^{+}$ (DCN$^{+}$)
could be positively identified. In reactions with NH$^{+}$ formation of
HCN$^{+}$ was clearly observed; the dependence of the HCN$^{+}$ normalized ion
yield on incident energy seems to indicate a threshold at about 40 eV which may
be due to an activation energy or an endothermicity of the surface reaction of
about 2.4-3.2 eV.

26
The categories of this paper are: bayes-an
10
The categories of this paper are: q-bio
33
The categories of this paper are: plasm-ph
15
The categories of this paper are: nucl-ex
19
The categories of this paper are: eess
14
The categories of this paper are: math-ph
1
The categories of this paper are: cs
17
The categories of this paper are: q-fin
22
The categories of this paper are: chao-dyn
4
The categories of this paper are: cond-mat
11
The categories of this paper are: hep-lat
16
The categories of this paper are: stat
12
The categories of this paper are: nucl-th
31
The categories of this paper are: ao-sci
23
The categories of this paper are: solv-int
6
The categories of this paper are: astro-ph