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.

We performed classical molecular dynamics simulations to model the scattering process of nitric oxide, NO, off graphene supported on gold. This is motivated by our desire to probe the energy transfer in collisions with graphene. Since many of these collision systems comprising of graphene and small molecules have been shown to scatter non‐reactively, classical molecular dynamics appear to describe such systems sufficiently. We directed thousands of trajectories of NO molecules onto graphene along the surface normal, while varying impact position, but also speed, orientation, and rotational excitation of the nitric oxide, and compare the results with experimental data. While experiment and theory do not match quantitatively, we observe agreement that the relative amount of kinetic energy lost during the collision increases with increasing initial kinetic energy of the NO. Furthermore, while at higher collision energies, all NO molecules lose some energy, and the vast majority of NO is scattered back, in contrast at low impact energies, the fraction of those nitric oxide molecules that are trapped at the surface increases, and some NO molecules even gain some kinetic energy during the collision process. The collision energy seems to preferentially go into the collective motion of the carbon atoms in the graphene sheet.

We report velocity-dependent internal energy distributions of nitric oxide molecules, NO, scattered off graphene supported on gold to further explore the dynamics of the collision process between NO radicals and graphene. These experiments were performed by directing a molecular beam of NO onto graphene in a surface-velocity map imaging setup, which allowed us to record internal energy distributions of the NO radicals as a function of their velocity. We do not observe bond formation but (1) major contributions from direct inelastic scattering and (2) a smaller trapping−desorption component where some physisorbed NO molecules have residence times on the order of microseconds. This is in agreement with our classical molecular dynamics simulations which also observe a small proportion of two-and multi-bounce collisions events but likewise a small proportion of NO radicals trapped at the surface for the entire length of the molecular dynamics simulations (a few picoseconds). Despite a collision energy of 0.31 eV, which would be sufficient to populate NO(v = 1), we do not detect vibrationally excited nitric oxide.