14. 05. 2026 13:00

Gustavo Diniz Silva, PhD » Sticking coefficient for atoms scattering on metallic surfaces

Department of Condensed Matter Physics, Charles University

Location: Lecture room F2, MFF UK (first floor, Ke Karlovu 5, Praha 2)

Achieving a complete understanding of the quantum dynamical processes that arise when an atom approaches a metallic surface remains a central challenge in surface physics. Conventional approaches based on the Born-Oppenheimer approximation become inadequated, since the atomic motion can couple to arbitrarily low-energy electronic excitations. In this work, we study the collision between an initially neutral hydrogen atom and a metallic copper surface represented by a half-filled conduction band. As the atom approaches the surface, the overlap between atomic and surface orbitals enables electron transfer to the hydrogen atom, inducing negative ionization and activating an image-charge potential that attracts the atom toward the surface. To describe this process, we introduce a generalized Anderson-impurity-like model that captures the essential physics of the collision, and we solve the total time-dependent Schrodinger equation to follow the evolution of the atomic wave packet. From the time-dependent dynamics, we compute the electronic contribution to the sticking coefficient, defined as the probability that the atom remains close to the surface after a long time, obtaining sticking probabilities as large as 27%. The simulations show that the creation of electron-hole pairs provides an efficient dissipation mechanism capable of absorbing sufficient kinetic energy from the incident particle to induce adsorption. Plotted as a function of the incident energy, the sticking coefficient exhibits a maximum, which we interpret as a compromise between the increasing strength of nonadiabatic processes and the decreasing time spent in the region where such processes occur. The numerical results are in a qualitative agreement with the available experimental data.
 
References:

[1]T. R. Knowles and H. Suhl, Physical Review Letters 39, 1417 (1977).     
[2] A. Abedi, N. T. Maitra, and E. K. U. Gross, J. Chem. Phys. 137, 22A530 (2012).
[3] G. Diniz. (2024). Sticking coefficient for atoms impinging on a metallic surface, and the x-ray photoemission by metals. Doctoral Thesis, University of São Paulo.   
[4] G. Diniz, C.R.C. Rêgo, E. K. U. Gross, and L. N. Oliveira, Sticking coefficient for atoms scattering on metallic surfaces, unpublished.
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