Isotopic effect for hydrogen atoms interacting with a cesiated surface

The interaction of deuterium atoms on a cesiated surface and the formation of hydrogen isotopologues molecules via the Eley-Rideal mechanism is studied using the computational setup recently adopted in the simulations of the same reactions for H atoms. The probability for scattering and adsorption processes on the surface as well as the mechanism underlying the reaction is pointed out for D atoms impinging on the surface in the same dynamical conditions previously used for H atoms. The isotopic effect in molecule formation is highlighted by considering the formation of D2 and HD molecules, this latter obtained by exchanging either the incoming or pre-adsorbed H atom with D isotope. Collisional data have been determined for two different adsorption sites on the surface. The recombination probabilities and coefficients for D2 and HD and the probabilities for other competitive surface processes have been determined. Internal states of isotopic molecules were solved and compared with those of H2 molecule formed on the same surface showing that the heteronuclear molecules are vibrationally more excited. A strong isotope mass effect emerged in the collision of D atom enhancing the probabilities for adsorption/desorption processes. Interestingly, deuterium atom impinging on the pre-adsorbed H atom on the surface increases the recombination probability, which anyway remains low.