The reflection-absorption infrared spectra of n-alkanes adsorbed on Pt(111)

Abstract

Reflection-absorption infrared spectra of the series of C 2 to C 6 normal alkanes in the form of both monolayers and multilayers on Pt(111) are presented. The spectra are interpreted to reveal the orientation of the plane containing the carbon chains to be almost exclusively parallel to the metal surface in the case of monolayers. The multilayers appeared to be crystalline again with molecules aligned so that the plane containing the carbon atoms was parallel to the substrate in the case of butane and hexane but with this plane at an angle to the surface in the case of pentane. The spectra of ethane and propane multilayers were consistent with liquid-like films. The monolayer spectra show evidence for infrared activity induced in some modes as a result of the metal-alkane interaction but there is no evidence for C-H … metal hydrogen bonding.