An inelastic neutron scattering spectroscopic investigation of the adsorption of ethene and propene on carbon

Inelastic neutron scattering (INS) spectra of ethene and propene adsorbed on carbon at ca. 20 K have been recorded and compared with the spectra of the solid alkenes. Differences between the alkenes in the INS spectra are attributed to the propene molecule experiencing less molecular recoil. Normal coordinate analysis reveals both alkenes to be present as physisorbed, disordered layers on carbon and that the interaction with the surface is weaker than in the corresponding crystal. On the basis of neutron powder diffraction measurements, the splitting in the =C-CH₃ torsion mode of solid propene is assigned to correlation field effects.