Deposition dynamics of Na monomers and dimers on an Ar(001) substrate

TL;DR

This study investigates how neutral and charged sodium atoms and dimers deposit on an argon surface, revealing charge effects on capture efficiency, penetration, and surface excitation, with implications for surface chemistry.

Contribution

It introduces a hierarchical modeling approach combining density-functional theory and molecular dynamics to analyze sodium deposition dynamics on argon surfaces, including charge effects.

Findings

Neutral Na is loosely captured at low impact energy.

Charged Na$^+$ penetrates the surface more effectively.

Charge enhances surface excitation and binding.

Abstract

We study deposition dynamics of Na and Na$_2$ on an Ar substrate, both species neutral as well as charged. The system is modeled by a hierarchical approach describing the Na valence electrons by time-dependent density-functional theory while Na core, Ar atoms and their dynamical polarizability are treated by molecular dynamics. We explore effects of Na charge and initial kinetic energy of the impinging Na system. We find that neutral Na is captured into a loosely bound adsorbate state for sufficiently low impact energy. The charged monomers are more efficiently captured and the cation Na$^+$ even penetrates the surface layer. For charged dimers, we come to different final configurations depending on the process, direct deposit of Na$_2^+$ as a whole, or sequential deposit. In any case, charge dramatically amplifies the excitation of the matrix, in particular at the side of the Ar dipoles. The presence of a charge also enhances the binding to the surface and favours accumulation of larger compounds.