Isotope and Surface Temperature Effects for Hydrogen Recombination on a Graphite Surface

Abstract

We highlight the isotope and surface temperature effects for hydrogen atom recombination on a graphite surface. The reaction dynamics is studied using the semiclassical collisional method, according to which the mass and temperature effects are due to the coupling between the H/D dynamics and the dynamics of the phonon excitation/de-excitation mechanism of the substrate. All possible collisional schemes with H/D adsorbed on the surface and H/D impinging from the gas phase are considered. In particular, we focus on the recombination reaction between an H atom colliding with a D atom adsorbed on the surface and a D atom incident on an H adatom. For H(2) and D(2) formation, the surface temperature effect is investigated by comparing the results obtained for T(S)=800 K with those obtained at T(S)=500 K and T(S)=100 K. Despite the low masses involved in the dynamics, effective isotope and temperature effects were observed on the recombination probabilities, reaction energetics, and roto-vibrational states of formed molecules. The results show the need for correct treatment of the multiphonon excitation mechanism in molecule-surface interactions.

Investigation of ZPE and temperature effects on the Eley–Rideal recombination of hydrogen atoms on graphene using a multidimensional graphene–H–H potential

“…It has been rightly argued that such characteristics are within the accuracy limits of current DFT functionals [6,11,18]. Accordingly, some works take a barrier into consideration with characteristics close to those determined by DFT calculations [9][10][11]15,17] while others consider reaction (1) as being barrier-less [1][2][3][4][5]7,8,[12][13][14][15][16]18] or nearly so [6]. The barrier in the Bachellerie-potential actually increases and moves closer towards the surface when the H b atom is displaced laterally away from the collinear approach (see Fig.…”

“…has been a subject of ongoing theoretical work over the past decade [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Interest in this topic was aroused from the astrophysical issue concerning H 2 formation in the interstellar medium (ISM).…”

Synergistic etch rates during low-energetic plasma etching of hydrogenated amorphous carbon

“…99,100 Since molecular hydrogen does not etch carbon, 101 a similarly high recombination probability for a-C:H would likewise contribute to a decrease in the etch rate. A high surface roughness, moreover, implies that hydrogen conversion occurs preferentially within the trenches and valleys of the roughness layer.…”

H∕D Recombination on Graphite and Tungsten: Collisional Data Relevant to Astrochemistry and Plasma-wall Interaction for Fusion

“…This reaction can be both an important channel for surface atom abstraction and an effective source of energetically activated molecules. The dynamics of H 2 formation on graphite has been investigated by us in great detail [2,3], some of the obtained collisional data will be presented in this contribution. The atom recombination catalyzed by surfaces can follow two basic mechanisms, the Langmuir-Hinshelwood (L-H) and the Eley-Rideal (E-R) reaction mechanism.…”