PNNL

Abstract

The adsorption, desorption, and clustering behavior of H20 on Pt(111) has been investigated by specular He scattering. The data show that water adsorbed on a clean Pt(111) surface undergoes a transition from a random to a clustered structure near 60 K. The initial helium scattering cross sections as a function of temperature are found to be insensitive to H20 flux over a range of 0.005 ML/s to 0.55 ML/s indicating the clustering process is more complex than simple surface diffusion. The coarsening process of an initially random distribution of water deposited at 25 K is found to occur over a broad temperature range, 60 K