^{1,2}, C. Crespos

^{2,a)}, P. Larrégaray

^{2}, J-C. Rayez

^{2}, L. Martin-Gondre

^{3}and J. Rubayo-Soneira

^{1}

### Abstract

Quasiclassical trajectories simulations are performed to study the influence of surface temperature on the dynamics of a N atom colliding a N-preadsorbed W(100) surface under normal incidence. A generalized Langevin surface oscillator scheme is used to allow energy transfer between the nitrogen atoms and the surface. The influence of the surface temperature on the N_{2} formed molecules via Eley-Rideal recombination is analyzed at T = 300, 800, and 1500 K. Ro-vibrational distributions of the N_{2} molecules are only slightly affected by the presence of the thermal bath whereas kinetic energy is rather strongly decreased when going from a static surface model to a moving surface one. In terms of reactivity, the moving surface model leads to an increase of atomic trapping cross section yielding to an increase of the so-called hot atoms population and a decrease of the direct Eley-Rideal cross section. The energy exchange between the surface and the nitrogen atoms is semi-quantitatively interpreted by a simple binary collision model.

I. INTRODUCTION

II. METHODOLOGY

III. RESULTS AND DISCUSSION

A. Results for the moving surfacemodel:Surface temperature effect

B. Energy transfer interpretation using a simple collision model

IV. CONCLUSIONS

### Key Topics

- Atom surface collisions
- 55.0
- Atom surface interactions
- 35.0
- Energy transfer
- 30.0
- Surface dynamics
- 29.0
- Interatomic potential energy surfaces
- 21.0

## Figures

Cross sections (in Å^{2}) for *bound* (bHA, circles), *metastable* (mHA, triangles) HA formation, and ER reaction (squares) obtained within a static surface model.

Cross sections (in Å^{2}) for *bound* (bHA, circles), *metastable* (mHA, triangles) HA formation, and ER reaction (squares) obtained within a static surface model.

Distribution of ER trajectories simulation time as a function of temperature. The initial kinetic energy of the incident atoms is 1.0 eV.

Distribution of ER trajectories simulation time as a function of temperature. The initial kinetic energy of the incident atoms is 1.0 eV.

Polar plot of the angular distribution of N_{2} formed molecules for different surface temperatures and a collision energy of the projectile atom: *E* _{ p } = 1.0 eV. Each distribution is normalized to unity.

Polar plot of the angular distribution of N_{2} formed molecules for different surface temperatures and a collision energy of the projectile atom: *E* _{ p } = 1.0 eV. Each distribution is normalized to unity.

Distributions of the total final energy, *E* _{ T }, (rotation + vibration + translation) of the N_{2} molecules for different collision energies of the projectile atom: *E* _{ p } = 1.0 eV (left) and *E* _{ p } = 2.6 eV (right) and for T = 0, 800, 1500 K. The maximum available final energy, , is indicated for each plot by a vertical line, which corresponds to the static surface model case. Lines are drawn to guide the eye.

Distributions of the total final energy, *E* _{ T }, (rotation + vibration + translation) of the N_{2} molecules for different collision energies of the projectile atom: *E* _{ p } = 1.0 eV (left) and *E* _{ p } = 2.6 eV (right) and for T = 0, 800, 1500 K. The maximum available final energy, , is indicated for each plot by a vertical line, which corresponds to the static surface model case. Lines are drawn to guide the eye.

Rotational (up) and vibrational (down) distributions of the formed N_{2} molecules for different kinetic energies of the projectile atom: *E* _{ p } = 1.0 eV (left) and *E* _{ p } = 2.6 eV (right). Each distribution is normalized to 1. The results are shown for different surface temperatures, as indicated. Lines are drawn to guide the eye.

Rotational (up) and vibrational (down) distributions of the formed N_{2} molecules for different kinetic energies of the projectile atom: *E* _{ p } = 1.0 eV (left) and *E* _{ p } = 2.6 eV (right). Each distribution is normalized to 1. The results are shown for different surface temperatures, as indicated. Lines are drawn to guide the eye.

Mean projectile kinetic energy as a function of trajectories integration time at various surface temperature for an initial kinetic energy of 1.0 eV.

Mean projectile kinetic energy as a function of trajectories integration time at various surface temperature for an initial kinetic energy of 1.0 eV.

Comparison between the projectile-surface energy transfer calculated using a simple collision modified Baule model (empty circles) and the results of the QCT simulations (plain square). Red lines indicate the maximum energy available for the formed molecule if no energy exchange with the surface is allowed.

Comparison between the projectile-surface energy transfer calculated using a simple collision modified Baule model (empty circles) and the results of the QCT simulations (plain square). Red lines indicate the maximum energy available for the formed molecule if no energy exchange with the surface is allowed.

(a) Potential energy (*Z* _{ p }, *b*) 2D-cut along the diagonal plane highlighted on the upper right panel where the coordinate system and W(100) unitary cell are presented. The Cartesian reference frame is originated on a Tungsten top surface atom (grey circles). Black circles represent nitrogen atoms. *Z* _{ p } and *Z* _{ t } stand, respectively, for the altitude of the projectile and the target atom. The parameter *b* is defined as the impact parameter. δ = 3.175 Å. Boltzmann thermal averaged (*Z* _{ p }, b) 2D-cut potentials for T = 800 (b) and 1500 K (c). Black lines correspond to zero energy isovalues (projectile atom at the infinite of the surface), red lines are positive values of the potentials, and blue dotted lines are negative values. The bold dotted lines encircle the most attractive regions of the potentials.

(a) Potential energy (*Z* _{ p }, *b*) 2D-cut along the diagonal plane highlighted on the upper right panel where the coordinate system and W(100) unitary cell are presented. The Cartesian reference frame is originated on a Tungsten top surface atom (grey circles). Black circles represent nitrogen atoms. *Z* _{ p } and *Z* _{ t } stand, respectively, for the altitude of the projectile and the target atom. The parameter *b* is defined as the impact parameter. δ = 3.175 Å. Boltzmann thermal averaged (*Z* _{ p }, b) 2D-cut potentials for T = 800 (b) and 1500 K (c). Black lines correspond to zero energy isovalues (projectile atom at the infinite of the surface), red lines are positive values of the potentials, and blue dotted lines are negative values. The bold dotted lines encircle the most attractive regions of the potentials.

## Tables

Exit channels cross sections (in Å^{2}) for static and moving surface models (T = 0, 300, 800, 1500 K) at two collision energies *E* _{ p } = 1.0 and 2.6 eV.

Exit channels cross sections (in Å^{2}) for static and moving surface models (T = 0, 300, 800, 1500 K) at two collision energies *E* _{ p } = 1.0 and 2.6 eV.

Energetics of direct ER reactions as a function of temperature. All energies of the table are given in eV.

Energetics of direct ER reactions as a function of temperature. All energies of the table are given in eV.

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