Analysis of the center of mass-, rotational- and intramolecular diffusive motions in a monolayer film of intermediate-length alkane molecules adsorbed on a solid surface

Abstract

The intramolecular diffusive motions associated with the creation and annihilation of gauche defects in intermediate-length alkane molecules adsorbed on a solid surface are relatively slow and on a time scale of nanoseconds. This has been shown by molecular dynamics (MD) simulations and by high-energy-resolution quasielastic neutron scattering (QNS) on monolayers of tetracosane (n-C24H50) adsorbed on graphite basal-plane surfaces. QNS with the high energy resolution makes it now possible to probe diffusive motions on the same time scale as in nuclear magnetic resonance (NMR) experiments and, in addition, to obtain information about length scales and character of motions through the wavevector dependence of the QNS.