It is widely believed that interactions at metal surfaces increase with an increase in molecular velocity. Scientists in California have presented findings that actually contradict this belief. [Nahler et al., Science, 321 (2008) 1191]
Studies in heterogenous catalysis, essentially the chemistry between two different phases i.e., solid, liquid, and gas began the more general study of surface science.
The Born-Oppenheimer (BO) Approximation which is the assumption that the electronic motion and the nuclear motion in molecules can be separated has contributed a great deal to the understanding of surface science and heterogenous catalysis.
There are however many cases where we see a breakdown in the BO approximation; many of these cases showing a decrease in excitation as the velocity of the molecules contacting the surface decrease.
Nahler et al, report when highly excited nitric oxide molecules are fired at the surface of a metal they witnessed greater molecular activity as the velocity of the incoming molecules decreased.
A simple model is presented to explain this observation, it suggests that it is not the motion of the nitric oxide molecules relative to the surface that effects this observation, but the relative vibrations of the N and O bond. As the bonds expand attraction to the surface metal become greater thus aiding molecular interactions, and at slow speeds the efficiency of this effect is enhanced.
Further work will take place to better understand the forces at play. This work will aid the understanding of the dynamics of molecules on metal surfaces.