One of the most abundant elements in the universe is silicon, and several studies have already been performed on their silicate forms. Nevertheless, few species with the SiO bond have been detected in the interstellar space [1][2]. Recently, spectroscopic techniques have detected SiS in some interstellar clouds, and SiO in minor amounts. These two diatomic molecules can be related to a depletio...

A novel ethynyl addition mechanism (EAM) has been established computationally as a practicable alternative to high-temperature hydrogen-abstraction-C2H2-addition (HACA) sequences to form polycyclic aromatic hydrocarbon (PAH) -like species under low-temperature conditions in the interstellar medium and in hydrocarbon-rich atmospheres of planets and their moons. Initiated by an addition of the et...

The chemical evolution of formamide (HCONH2), a molecule of astrobiological interest that has been tentatively identified in interstellar ices and in cometary coma, has been studied in laboratory under simulated astrophysical conditions such as ion irradiation at low temperature.

In the diffuse interstellar medium a molecule experiences isolation conditions that cannot (yet?) be achieved in the laboratory. In such conditions its rotation is dominated by the interaction with the radiation field through a complex statistical equilibrium. This problem has been analyzed numerically with MonteCarlo techniques, for a simplified PAH molecule model. As a possible application, t...

Molecular hydrogen is the most abundant molecule in the universe. It is the first one to form and survive photo-dissociation in tenuous environments. Its formation involves catalytic reactions on the surface of interstellar grains. The micro-physics of the formation process has been investigated intensively in the last 20 years, in parallel of new astrophysical observational and modeling progre...

We present a model for the hydrogenation states of Polycyclic Aromatic Hydrocarbons (PAHs) in the diffuse interstellar medium. First, we study the abundance of hydrogenation and charge states of PAHs due to photo-ionization, photodissociation in the interstellar UV field, electron recombination and chemical reactions between PAH cations and H or H2. For PAH cations, we find that the dehydrogena...

The reaction of ground-state carbon atoms with acetylene was studied under single-collision conditions in crossed beam experiments to investigate the chemical dynamics of forming cyclic and linear C3H isomers (c-C3H and l-C3H, respectively) in interstellar environments via an atom-neutral reaction. Combined state-of-the-art ab initio calculations and experimental identification of the carbon-hy...

We present an improved model for the absorption of X-rays in the interstellar medium (ISM) intended for use with data from future X-ray missions with larger effective areas and increased energy resolution such as Chandra and the X-ray Multiple Mirror mission, in the energy range & 100 eV. Compared to previous work, our formalism includes recent updates to the photoionization cross section and r...