Dynamics of Methane Monolayers Adsorbed on Graphite

Abstract
Pulsed-NMR measurements of methane on graphite have been performed between 45 and 105 K for 0.2 to 1.1 monolayers. Spin-relaxation times show first-order melting at 57 K, sensitivity to the hypercritical fluid, and continuous transitions where an incommensurate solid displaces the registered phase at both higher temperature and coverage. These measurements, plus activation-energy comparisons, provide a significant clarification of methane's high-temperature behavior.