title: Interaction of D2 with H2O amorphous ice studied by temperature-programmed desorption experiments.
abstract: The gas-surface interaction of molecular hydrogen D2 with a thin film of porous amorphous solid water (ASW) grown at 10 K by slow vapor deposition has been studied by temperature-programmed-desorption (TPD) experiments. Molecular hydrogen diffuses rapidly into the porous network of the ice. The D2 desorption occurring between 10 and 30 K is considered here as a good probe of the effective surface of ASW interacting with the gas. The desorption kinetics have been systematically measured at various coverages. A careful analysis based on the Arrhenius plot method has provided the D2 binding energies as a function of the coverage. Asymmetric and broad distributions of binding energies were found, with a maximum population peaking at low energy. We propose a model for the desorption kinetics that assumes a complete thermal equilibrium of the molecules with the ice film. The sample is characterized by a distribution of adsorption sites that are filled according to a Fermi-Dirac statistic law. The TPD curves can be simulated and fitted to provide the parameters describing the distribution of the molecules as a function of their binding energy. This approach contributes to a correct description of the interaction of molecular hydrogen with the surface of possibly porous grain mantles in the interstellar medium.
authors.affiliation: LERMA-LAMAp, CNRS UMR 8112, Université de Cergy-Pontoise et Observatoire de Paris, 5 Mail Gay-Lussac, F-95031 Cergy-Pontoise Cedex, France.
authors.forename: L
authors.initials: L
authors.lastname: Amiaud
authors.forename: J H
authors.initials: JH
authors.lastname: Fillion
authors.forename: S
authors.initials: S
authors.lastname: Baouche
authors.forename: F
authors.initials: F
authors.lastname: Dulieu
authors.forename: A
authors.initials: A
authors.lastname: Momeni
authors.forename: J L
authors.initials: JL
authors.lastname: Lemaire