Isotopic effect for hydrogen atoms interacting with a cesiated surface

Abstract

The interaction of deuterium atoms on a cesiated surface and the formation of hydrogen isotopologue molecules via the Eley-Rideal mechanism is studied using the computational set-up recently adopted in 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 shown 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 D 2 and HD molecules; this latter is obtained by exchanging either the incoming or pre-adsorbed H atom with a D isotope. Collisional data have been determined for two different adsorption sites on the surface. The recombination probabilities and coefficients for D 2 and HD and the probabilities of other competitive surface processes have been determined. Internal states of isotopic molecules were solved and compared with those of H 2 molecules formed on the same surface showing that the heteronuclear molecules are vibrationally more excited. A strong isotope mass effect emerged in the collision of the D atom enhancing the probabilities for adsorption/desorption processes. Interestingly, a D atom impinging on the pre-adsorbed H atom on the surface increases the recombination probability, which remains low nonetheless.

Negative ion source operation with deuterium

“…The larger mass of deuterons may also remove Cs from the PG more rapidly than protons. A molecular dynamic calculation result predicts that the difference in surface adsorption energies between the two isotopes is small [148]. But the larger mass of deuterons increases the removal of Cs, other adsorbates and Mo from the PG surface [149].…”

Deterministic models of minority neutral particle kinetics close to a catalytic surface, based on the formalism of radiative transfer

“…An important example in the emerging field of plasma catalysis [20][21][22] is the distribution of the impact angles of neutral species with the catalytic surface. This distribution is essential in the determination of scattering and reaction probabilities, using microscopic methods such as semi-classical or ab initio molecular dynamics [23][24][25]. While an estimate of this function can be provided starting from the concentration gradients in a macroscopic approach, the present method (and MC simulations) allows accurate calculations.…”