Related papers: H$_2$ ortho-para spin conversion on inhomogeneous …
We present a computational study into the adsorption properties of CO$_2$ on amorphous and crystalline water surfaces under astrophysically relevant conditions. Water and carbon dioxide are two of the most dominant species in the icy…
The spatial distribution of the chemical reservoirs in protoplanetary disks is key to elucidate the composition of planets, especially habitable ones. However, the partitioning of the main elements among the refractory and volatile phases…
Despite the low elemental deuterium abundance in the Galaxy, enhanced molecular D/H ratios have been found in the environments of low-mass star forming regions, and in particular the Class 0 protostar IRAS 16293-2422. The CHESS (Chemical…
First-principles calculations based on density functional theory and the pseudopotential method have been used to investigate the energetics of H$_2$O adsorption on the (110) surface of TiO$_2$ and SnO$_2$. Full relaxation of all atomic…
We report the results of spectroscopic mapping observations carried out toward the Herbig-Haro objects HH7-11 and HH54 over the 5.2 - 37 micron region using the Infrared Spectrograph of the Spitzer Space Telescope. These observations have…
Except for ortho- and para-H2, very little is known about nuclear spin isomers (or spin modifications) of molecules. The main reason is the lack of practical enrichment techniques. Recently a few enrichment methods were developed, which…
H$_2$O is a key molecule in characterizing atmospheres of temperate terrestrial planets, and observations of transmission spectra are expected to play a primary role in detecting its signatures in the near future. The detectability of…
State-selected total cross sections and thermal rate coefficients are computed for the HD + $ortho$-/$para$-H$_2$ rotational energy transfer collision at low temperatures: 2 K $\lesssim$ T $\lesssim$ 300 K. A modified H$_2$-H$_2$ potential…
Molecular hydrogen is the most abundant molecular species in the Universe. While no doubts exist that it is mainly formed on the interstellar dust grain surfaces, many details of this process remain poorly known. In this work, we focus on…
We present Herschel/HIFI observations of the fundamental rotational transitions of ortho- and para-H$_2^{16}$O and H$_2^{18}$O in absorption towards Sagittarius~B2(M) and W31C. The ortho/para ratio in water in the foreground clouds on the…
The $\mathrm{H}_2$ formation on grains is known to be sensitive to dust temperature, which is also known to fluctuate for small grain sizes due to photon absorption. We aim at exploring the consequences of simultaneous fluctuations of the…
We study the formation of molecular hydrogen on dust grain surfaces and apply our results to the high redshift universe. We find that a range of physical parameters, in particular dust temperature and gas temperature, but not so much dust…
We study the changes in physical and chemical conditions during the collapse of a pre--protostellar core, starting from initial conditions appropriate to a dense molecular cloud and proceeding to the ``completely depleted'' limit. We follow…
Methods: The microscopic equations of H2-formation and protonation are integrated numerically over time in such a manner that the overall structures evolve self-consistently under benign conditions. Results: The equilibrium H2 formation…
Grain surfaces play a central role in the formation and desorption of molecules in space. To form molecules on a grain surface, adsorbed species trapped in binding sites must be mobile and migrate to adjacent sites. Thermal hopping is a…
[Abridged] Observations of protoplanetary disks suggest that they are depleted in gas-phase CO. It has been posed that gas-phase CO is chemically consumed and converted into less volatile species through gas-grain processes. Observations of…
In the interstellar clouds, molecular hydrogens are formed from atomic hydrogen on grain surfaces. An atomic hydrogen hops around till it finds another one with which it combines. This necessarily implies that the average recombination…
Multi-hydrogenated species with proper symmetry properties can present different spin configurations, and thus exist under different spin symmetry forms, labeled as para and ortho for two-hydrogen molecules. We investigated here the…
The water molecule occurs in two nuclear-spin isomers that differ by the value of the total nuclear spin of the hydrogen atoms, i.e., $I=0$ for para-H$_2$O and $I=1$ for ortho-H$_2$O. Spectroscopic transitions between rovibrational states…
The feasibility of contemporary gas-grain astrochemical models depends on the availability of accurate kinetics data, in particular, for surface processes. We study the sensitivity of gas-grain chemical models to the energy barrier Ea of…