Vibrational spectroscopy of water molecules on Pt(111) at submonolayer coverages

The adsorption behavior and vibrational dynamics of H2O (D2O) molecules on the Pt(111) surface at surface temperatures, T-s, between 20 and 140 K have been investigated using high-resolution helium atom scattering. At T-s40 K, water monomers are adsorbed on the surface, whereas at T-s>40 K, the water molecules cluster to form stable dimers or trimers. At higher temperatures of about 100-130 K, water adsorbs in large two-dimensional ice bilayer islands. From time-of-flight measurements the low-frequency external vibrations of the water monomers, dimers and 2D islands were determined, demonstrating substantial differences for these three water-binding configurations. (C) 1999 Elsevier Science B.V. All rights reserved.