Nitric Oxide Scattering off Graphene Using Surface-Velocity Map Imaging

Abstract

We investigated the scattering of nitric oxide, NO, off graphene supported on gold. This is of fundamental importance to chemistry as collisions are the necessary first step to chemical reactions on graphene, and nitric oxide molecules are inherently radicals, with the potential to bond to graphene. We directed a molecular beam of NO in helium onto graphene and detected the directly scattered molecules using surface-velocity map imaging. In contrast to previous scattering studies off graphite, which detected only a modest reduction of the translational energy of the NO, we observe a loss of ∼80% of the molecules’ kinetic energy. Our classical molecular dynamics simulations still predict a loss of ∼60% of the translational energy in the scattering process. This energy appears to partly go into the NO rotations but mostly into collective motion of the carbon atoms in the graphene sheet. At 0° incidence angle, we also observe a very narrow angular scattering distribution. Both findings may be unique to pristine graphene on gold as (1) the two-dimensional (2D) honeycomb structure is perfectly flat and (2) the graphene is only loosely held to the gold at a distance of 3.4 Å, thus it can absorb much of the projectiles’ kinetic energy.