Energy Dissipation to Tungsten Surfaces upon Eley–Rideal Recombination of N₂ and H₂

Abstract

Quasiclassical molecular dynamics simulations are performed to investigate energy dissipation to the (100) and (110) tungsten surfaces upon Eley−Rideal (ER) recombination of H 2 and N 2 . Calculations are carried out within the single adsorbate limit under normal incidence. A generalized Langevin surface oscillator (GLO) scheme is used to simulate the coupling to phonons, whereas electron−hole (e-h) pair excitations are implemented using the local density friction approximation (LDFA). Phonon excitations are found to reduce the ER reactivity for N 2 recombination, but do not affect H abstraction. In contrast, the effect of e-h pair excitations on the ER recombination cross section is small for N 2 , but can be important for H 2 . The analysis of the energy lost by the recombined species shows that most of the energy is dissipated into phonon excitations in the N 2 recombination and into electronic excitations in the H 2 recombination. In all cases, the energy dissipated into e-h pairs is taken away from the translational kinetic energy of the formed molecules, whereas dissipation to phonons, only significant for N 2 , also affects vibration. Interestingly, the electron mediated energy losses are found to be smaller in the case of N 2 when surface motion is allowed.

Communication: Hot-atom abstraction dynamics of hydrogen from tungsten surfaces: The role of surface structure

“…43,44 Secondary HA abstraction is accordingly also more efficient on W(110). As observed in the single adsorbate limit, 35,37 ER abstraction proceeds, on the W(100) surface, via collision of the projectiles not only with neighbouring W surface atoms on the top most layer but also with second layer W atoms. A similar difference between the two surfaces is observed in the J. Chem.…”

“…31 The influence of the crystal face has been recently scrutinized theoretically for the Eley-Rideal (ER) recombination a) pascal.larregaray@u-bordeaux.fr of hydrogen and nitrogen on the W(100) and W(110) surfaces, [32][33][34][35][36] accounting for dissipation to surface phonons and electrons. 37 In these direct ultrafast processes, the surface is thought to mostly behave as a spectator. Nevertheless, significant differences in the abstraction mechanisms and cross sections have been predicted, stemming from the distinct topologies of the interactions upon approach of the projectile towards the target.…”

“…Dissipation has been found to quantitatively affect N 2 reactivity but only marginally that of H 2 . 37 Though extended knowledge has been gathered on ER abstraction, pioneering molecular dynamics simulations [38][39][40] and comparisons between kinetics experiments and models 18,38,41,42 have suggested hydrogen abstraction to essentially proceed via the HA process for various metals. Recent theoretical works have thus focused on this issue, in particular for H 2 recombining from W(110).…”

“…[45][46][47][48] As a result of H-atom scattering, recombination may occur via three different processes: ER abstraction is assumed when the formed molecule moves definitively toward the vacuum after the first rebound of the projectile. 37 Otherwise, abstraction is considered as primary HA process. Whenever abstraction involves two target atoms, it is classified as a secondary HA process.…”

Femtosecond-laser-driven molecular dynamics on surfaces: Photodesorption of molecular oxygen from Ag(110)

“…II D below. The LDFA has been applied to study the effect of electronic excitations in the dynamics of atoms and molecules on metal surfaces [38,[45][46][47][48][49][50]. The scattering of heated electrons with the adsorbate results also in a fluctuating force R el i [see Eq.…”