  Using the King & Wells method, we present experimental data on the dependence
of the sticking of molecular hydrogen and deuterium on the beam temperature
onto non- porous amorphous solid water (ASW) ice surfaces of interstellar
interest. A statistical model that explains the isotopic effect and the beam
temperature behavior of our data is proposed. This model gives an understanding
of the discrepancy between all known experimental results on the sticking of
molecular hydrogen. Moreover it is able to fit the theoretical results of V.
Buch et al. [Astrophys. J. (1991), 379, 647] on atomic hydrogen and deuterium.
For astrophysical applications, an analytical formula for the sticking
coefficients of H, D, H2, D2 and HD in the case of a gas phase at thermal
equilibrium is also provided at the end of the article.
