Breaking through the glass ceiling: The correlation between the self-diffusivity in and krypton permeation through deeply supercooled liquid nanoscale methanol films

摘要

Molecular beam techniques, temperature-programmed desorption (TPD), and reflection absorptioninfrared spectroscopy (RAIRS) are used to explore the relationship between krypton permeationthrough and the self-diffusivity of supercooled liquid methanol at temperatures (100-115 K) nearthe glass transition temperature, Tg (103 K). Layered films, consisting of CH3OH and CD3OH, aredeposited on top of a monolayer of Kr on a graphene covered Pt(111) substrate at 25 K. ConcurrentKr TPD and RAIRS spectra are acquired during the heating of the composite film to temperaturesabove Tg. The CO vibrational stretch is sensitive to the local molecular environment and is used todetermine the supercooled liquid diffusivity from the intermixing of the isotopic layers. We find thatthe Kr permeation and the diffusivity of the supercooled liquid are directly and quantitativelycorrelated. These results validate the rare-gas permeation technique as a tool for probing thediffusivity of supercooled liquids.