Hydrocarbon trapping and condensation on Pt(111)

A direct, reflected beam method under ultrahigh-vacuum conditions was used to measure the sticking coefficient of several small hydrocarbon molecules (methylcyclohexane, cyclohexane, toluene, benzene, and methanol) on clean and adsorbate-covered Pt(111) surfaces and on the molecular solid phases that can be formed at temperatures below that required for multilayer sublimation. We find that the sticking coefficient for all of these molecules on the clean Pt(111) surface and the molecular solid phase at 100 K is unity. The simple, classical hard-cube model provides a useful way to understand this behavior.