Thermal reduction of activation energy of tricyclohexylphosphine on a rhodium crystal surface

The activation energy of desorption of molecules adsorbed on crystal surfac es is defined by the interaction potential. This potential is reduced for f inite temperature because of phonon excitations of the crystal surface. Mor eover, rotations of molecules relative to the crystal surface contribute to the thermal reduction of the activation energy. As an application we consi der organic phosphines on a rhodium surface. We interpolate the interaction by the Morse potential with parameters fitted to data obtained by density functional theory. The theoretical results are compared to temperature-prog rammed desorption experiments of tricyclohexylphosphine adsorbates on the r hodium crystal surface. The activation energy of desorption of the monolaye rs are calculated from temperature programmed desorption studies using the Redhead equation. (C) 2001 American Institute of Physics.