Ordering and Dynamics of CN$^{-}$/Cu(001) Surfaces

C$_{2}$N$_{2}$ adsorption on Cu(001) is largely dissociative, yielding adsorbed CN$^{-}$ species. Exposure dependent angular-resolved Helium Atom Scattering (HAS) measurements show the initial development of a diffuse backscattered intensity, followed by the onset of c(10x6) superstructure domain growth only in a limited exposure temperature range. Diffraction from an ordered phase is not observed for exposures above 323K, nor below 223K. Yet, even at optimal deposition temperatures, a diffuse scattering contribution remains at saturation and persists beyond 473K. Energy and angular resolved measurements show that the diffuse He intensity is strongly inelastic, and multiphonon-like; i.e. not showing features with resolvable discrete energies. The surface temperature and momentum exchange dependencies of this intensity will elaborate the nature of the dynamics of CN$^{-}$ on Cu(001) surfaces. The CN$^{-}$ coverage dependence of the inelastic intensity also illustrates the influence of intermolecular interactions in CN$^{-}$ motion.