Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Electron-impact excitation of diatomic hydride cations II: OH$^+$ and
  SH$^+$   R-matrix calculations combined with the adiabatic-nuclei-rotation and
Coulomb-Born approximations are used to compute electron-impact rotational rate
coefficients for two open-shell diatomic cations of astrophysical interest: the
hydoxyl and sulphanyl ions, OH$^+$ and SH$^+$. Hyperfine resolved rate
coefficients are deduced using the infinite-order-sudden approximation. The
propensity rule $\Delta F=\Delta j=\Delta N=\pm 1$ is observed, as is expected
for cations with a large dipole moment. A model for OH$^+$ excitation in the
Orion Bar photon-dominated region (PDR) is presented which nicely reproduces
Herschel observations for an electron fraction $x_e=10^{-4}$ and an OH$^+$
column density of $3\times 10^{13}$~cm$^{-2}$. Electron impact electronic
excitation cross sections and rate coefficients for the ions are also
presented.

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The categories of this paper are: hep-ph
3
The categories of this paper are: physics
36
The categories of this paper are: cmp-lg
33
The categories of this paper are: plasm-ph
4
The categories of this paper are: cond-mat
9
The categories of this paper are: nlin
14
The categories of this paper are: math-ph
20
The categories of this paper are: acc-phys
17
The categories of this paper are: q-fin
2
The categories of this paper are: math
18
The categories of this paper are: econ
34
The categories of this paper are: chem-ph
24
The categories of this paper are: dg-ga
21
The categories of this paper are: adap-org
13
The categories of this paper are: quant-ph
22
The categories of this paper are: chao-dyn