Electron-impact excitation of diatomic hydride cations II: OH${}^{+}$ and SH${}^{+}$

Abstract

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.

8 pages, 5 figures, 6 tables, accepted for publication in MNRAS

References in corpus (10)

• The chemistry of ions in the Orion Bar I. - CH+, SH+, and CF+: The effect of high electron density and vibrationally excited H2 in a warm PDR surface
• State-to-state chemistry and rotational excitation of CH${}^{+}$ in photon-dominated regions
• OH+ in astrophysical media: state-to-state formation rates, Einstein coefficients and inelastic collision rates with He
• OH+ and H2O+ absorption toward PKS1830-211
• Herschel / HIFI spectral line survey of the Orion Bar - Temperature and density differentiation near the PDR surface
• Near threshold rotational excitation of molecular ions by electron-impact
• Detection of CH+, SH+, and their 13C- and 34S- isotopologues toward PKS1830-211
• Herschel Planetary Nebula Survey (HerPlaNS) - First Detection of OH+ in Planetary Nebulae
• Revised spectroscopic parameters of SH${}^{+}$ from ALMA and IRAM 30 m observations
• Inelastic low-energy collisions of electrons with HeH${}^{+}$: rovibrational excitation and dissociative recombination

Cited by in corpus (5)

• Photodissociation and X-Ray Dominated Regions
• Bottlenecks to interstellar sulfur chemistry: Sulfur-bearing hydrides in UV-illuminated gas and grains
• Hyperfine excitation of SH${}^{+}$ by H
• Dissociative Recombination of Rotationally Cold OH${}^{+}$ and Its Implications for the Cosmic Ray Ionization Rate in Diffuse Clouds
• Laser-probing the rotational cooling of molecular ions by electron collisions