The influence of the surface state onto the distance distribution of single molecules and small molecular clusters

We investigate the distance distribution of two anorganic molecules (CO, H2O), one organic radical (para-benzyne), and one strongly dipolar molecule (ortho-dinitrobenzene) on the (111) faces of copper and silver. Above the onset of diffusion, their distribution is influenced by the surface state and oscillates. While CO, H2O, and para-benzyne show the expected oscillation period of ≈λF/2, ortho-dinitrobenzene oscillates with λF/4. The position of the first maximum in these oscillations is consistent with a perfect scatterer for the anorganic molecules, but inconsistent for the radical and the dipolar molecule. This observation is utilized to explain the double periodicity observed in the distance distribution of ortho-dinitrobenzene.