Related papers: Rotational equilibrium of C$_2$ in diffuse interst…
Newly-computed collisional rate coefficients for the excitation of C$_2$ in collisions with H$_2$, presented recently by Najar and Kalugina (2020), are significantly larger than the values adopted previously in models for the excitation of…
Chloronium (H$_2$Cl$^+$) is an important intermediate of Cl-chemistry in space. The accurate knowledge of its collisional properties allows a better interpretation of the corresponding observations in interstellar clouds and therefore a…
We present spectroscopic observations obtained with the infrared Spitzer Space Telescope, which provide insight into the H$_2$ physics and gas energetics in photodissociation Regions (PDRs) of low to moderate far-ultraviolet (FUV) fields…
Using high-resolution (~85000) and high signal-to-noise ratio (~200) optical spectra acquired with the European Southern Observatory Ultraviolet and Visual Echelle Spectrograph, we have determined the interstellar column densities of C2 for…
A basic model for the formation of non-equilibrium rotational energy distributions is described for reactive, homo-polar diatomic molecules and ions in the interstellar medium. Kinetic models were constructed to calculate the rotational…
We probe the physical conditions in high-redshift damped Ly-alpha systems using the observed molecular fraction and the rotational excitation of molecular hydrogen. We report two new detections of H2 at z = 2.402 and 1.989 toward,…
The detection of CF$^+$ in interstellar clouds potentially allows astronomers to infer the elemental fluorine abundance and the ionization fraction in ultraviolet-illuminated molecular gas. Because local thermodynamic equilibrium (LTE)…
Motivated by recent observations with Herschel/PACS, and the availability of new rate coefficients for the collisional excitation of CO (Yang et al. 2010), the excitation of warm astrophysical CO is revisited with the use of numerical and…
The modelling of emission spectra of molecules seen in interstellar clouds requires the knowledge of collisional rate coefficients. Among the commonly observed species, N$_2$H$^+$ is of particular interest since it was shown to be a good…
Utilising previous work by the authors on the spin-coupled rotational cross-sections for electron-CN collisions, data for the associated rate coefficients is presented. Data on rotational, fine-structure and hyperfine-structure transition…
We present LVG and non-local radiative transfer calculations involving the rotational and hyperfine structure of the spectrum of N$_2$H$^+$ with collisional rate coefficients recently derived by us. The goal of this study is to check the…
We report the derivation of rate coefficients for the rotational (de-)excitation of PO$^+$ induced by collisions with H$_2$. The calculations were performed on a four-dimensional potential energy surface, obtained on top of highly accurate…
Aims. We model a diffuse molecular cloud present along the line of sight to the star HD 102065. We compare our modeling with observations to test our understanding of physical conditions and chemistry in diffuse molecular clouds. Methods.…
We have used archival far-ultraviolet spectra from observations made by HST/STIS and FUSE to determine the column densities and rotational excitation temperatures for CO and H2, respectively, along the lines of sight to 23 Galactic O and B…
We consider collisional excitation of H$_2$ molecules in C-type shocks propagating in dense molecular clouds. New data on collisional rate coefficients for (de-)excitation of H$_2$ molecule in collisions with H atoms and new H$_2$…
We present a detailed theoretical study of the rotational excitation of CH$^+$ due to reactive and nonreactive collisions involving C$^+(^2P)$, H$_2$, CH$^+$, H and free electrons. Specifically, the formation of CH$^+$ proceeds through the…
We use far-UV absorption spectra obtained with FUSE towards three late B stars to study the formation and excitation of H2 in the diffuse ISM. The data interpretation relies on a model of the chemical and thermal balance in…
The H$_2$+H$_2$ system has long been considered as a benchmark system for ro-vibrational energy transfer in bimolecular collisions. However, most studies thus far have focused on collisions involving H$_2$ molecules in the ground…
OH is a cornerstone molecule in the chemistry of interstellar and circumstellar media and is ubiquitously detected in warm gas thanks to its infrared rotational lines. However, the excitation processes of OH remain poorly characterized. We…
We present three-dimensional astrochemical simulations and synthetic observations of magnetised, turbulent, self-gravitating molecular clouds. We explore various galactic interstellar medium environments, including cosmic-ray ionization…