OH+ in astrophysical media: state-to-state formation rates, Einstein coefficients and inelastic collision rates with He

Abstract

The rate constants required to model the OH${}^{+}$ observations in different regions of the interstellar medium have been determined using state of the art quantum methods. First, state-to-state rate constants for the H${}_2(v=0,J=0,1)$+ O${}^{+}$(${}^{4}S$) $\to$ H + OH${}^{+}(X^3{\Sigma }^{-},v^{\prime },N)$ reaction have been obtained using a quantum wave packet method. The calculations have been compared with time-independent results to asses the accuracy of reaction probabilities at collision energies of about 1 meV. The good agreement between the simulations and the existing experimental cross sections in the $0.01-$1 eV energy range shows the quality of the results. The calculated state-to-state rate constants have been fitted to an analytical form. Second, the Einstein coefficients of OH${}^{+}$ have been obtained for all astronomically significant ro-vibrational bands involving the $X^3{\Sigma }^{-}$ and/or $A^3\Pi$ electronic states. For this purpose the potential energy curves and electric dipole transition moments for seven electronic states of OH${}^{+}$ are calculated with {\it ab initio} methods at the highest level and including spin-orbit terms, and the rovibrational levels have been calculated including the empirical spin-rotation and spin-spin terms. Third, the state-to-state rate constants for inelastic collisions between He and OH${}^{+}(X^3{\Sigma }^{-})$ have been calculated using a time-independent close coupling method on a new potential energy surface. All these rates have been implemented in detailed chemical and radiative transfer models. Applications of these models to various astronomical sources show that inelastic collisions dominate the excitation of the rotational levels of OH${}^{+}$. In the models considered the excitation resulting from the chemical formation of OH${}^{+}$ increases the line fluxes by about 10 % or less depending on the density of the gas.

References in corpus (32)

• An atomic and molecular database for analysis of submillimetre line observations
• A model for atomic and molecular interstellar gas: The Meudon PDR code
• Investigating the Cosmic-Ray Ionization Rate in the Galactic Diffuse Interstellar Medium through Observations of H3+
• Black hole accretion and star formation as drivers of gas excitation and chemistry in Mrk231
• H3+ in Diffuse Interstellar Clouds: a Tracer for the Cosmic-Ray Ionization Rate
• Molecular excitation in the Interstellar Medium: recent advances in collisional, radiative and chemical processes
• Water in Star-Forming Regions with the Herschel Space Observatory (WISH): Overview of key program and first results
• The Chemistry of Interstellar OH+, H2O+, and H3O+: Inferring the Cosmic Ray Ionization Rates from Observations of Molecular Ions
• Interstellar OH+, H2O+ and H3O+ along the sight-line to G10.6-0.4
• Herschel/HIFI observations of interstellar OH+ and H2O+ towards W49N: a probe of diffuse clouds with a small molecular fraction
• Diagnostics of AGN-driven Molecular Outflows in ULIRGs from Herschel-PACS Observations of OH at 119um
• Surface chemistry in the interstellar medium - I - H2 formation by Langmuir-Hinshelwood and Eley-Rideal mechanisms
• Oxygen Chemistry in the Circumstellar Envelope of the Carbon-Rich Star IRC+10216
• Comparative study of CH+ and SH+ absorption lines observed towards distant star-forming regions
• Detection of circumstellar CH2CHCN, CH2CN, CH3CCH and H2CS
• Excited OH+, H2O+, and H3O+ in NGC 4418 and Arp 220
• 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
• Hydrides in Young Stellar Objects: Radiation tracers in a protostar-disk-outflow system
• Nitrogen hydrides in the cold envelope of IRAS16293-2422
• Herschel observations of the Sgr B2 cores: Hydrides, warm CO, and cold dust
• A complete model of CH+ rotational excitation including radiative and chemical pumping processes
• Far-Infrared Spectroscopy of the Galactic Center. Hot Molecular Gas: Shocks versus Radiation near SgrA*
• Spatially extended OH+ emission from the Orion Bar and Ridge
• Detection of anhydrous hydrochloric acid, HCl, in IRC+10216 with the Herschel SPIRE and PACS spectrometers
• First detection of the Methylidyne cation (CH+) fundamental rotational line with the Herschel/SPIRE FTS
• The widespread occurence of water vapor in the circumstellar envelopes of carbon-rich AGB stars: first results from a survey with Herschel/HIFI
• Ro-vibrational CO Detected in the $\beta$~Pictoris Circumstellar Disk
• Variations in H2O+/H2O ratios toward massive star-forming regions
• OH+ in Diffuse Molecular Clouds
• Kinematics of the ionized-to-neutral interfaces in Monoceros R2
• Herschel Planetary Nebula Survey (HerPlaNS) - First Detection of OH+ in Planetary Nebulae
• Herschel spectral-mapping of the Helix Nebula (NGC 7293): Extended CO photodissociation and OH+ emission

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• Interstellar Hydrides
• State-to-state chemistry and rotational excitation of CH${}^{+}$ in photon-dominated regions
• Electron-impact excitation of diatomic hydride cations I: HeH${}^{+}$, CH${}^{+}$, ArH${}^{+}$
• WISH VI. Constraints on UV and X-ray irradiation from a survey of hydrides in low- to high-mass YSOs
• An efficient statistical method to compute molecular collisional rate coefficients
• Formation of interstellar SH${}^{+}$ from vibrationally excited H${}_2$: Quantum study of S${}^{+}$ + H${}_2$ $\rightleftarrows$ SH${}^{+}$ + H reactions and inelastic collisions
• The ionization rates of galactic nuclei and disks from Herschel/HIFI observations of water and its associated ions
• The role of highly vibrationally excited H2 initiating the N chemistry: Quantum study and 3-sigma detection of NH emission in the Orion Bar PDR
• Electron-impact excitation of diatomic hydride cations II: OH${}^{+}$ and SH${}^{+}$
• H${}_3^{+}$ absorption and emission in local U/LIRGs with JWST/NIRSpec: Evidence for high H${}_2$ ionization rates
• Knowledge Gaps in the Cometary Spectra of Oxygen-Bearing Molecular Cations
• Laser Scheme for Doppler Cooling of the Hydroxyl Cation (OH${}^{+}$)