He-Scattering Investigation of CO Migration on Pt(111)

The capability of a He-scattering experiment to detect the migration of adsorbed molecules on monocrystal surfaces is demonstrated for the first time. CO migration and island formation can be investigated at very low coverages because of the very large cross section for He scattering of CO adsorbed on Pt(111). The activation energy for CO migration on Pt(111) is found to be 7 kcal/mole. No island formation at low CO coverages on a defect-free Pt(111) surface was detected in the temperature range 120-400 K.