ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
We have studied the interaction of cyclobutane with the hexagonally close-packed Ru(001) surface. High-resolution electron energy loss spectroscopy (HREELS) has been used to identify the vibrational modes of both c-C4H8 and c-C4D8 adsorbed at 90 K as a function of cyclobutane exposure. We have observed a vibrational mode not observed in the gas phase at 2600 cm−1 (2140 cm−1) which is attributed to the strong interaction of the cyclobutane C–H (C–D) bonds with the ruthenium surface. Two different adsorption geometries for cyclobutane on Ru(001) have been proposed based on the dipolar activity of this softened C–H mode. We have also measured the trapping-mediated dissociative chemisorption of both c-C4H8 and c-C4D8 at surface temperatures between 190 and 1200 K. The measured activation energies with respect to the bottom of the physically adsorbed well for c-C4H8 and c-C4D8 are 10 090±180 and 10 180±190 cal/mol, respectively. The trapping-mediated chemisorption of cyclobutane is believed to occur via C–C bond cleavage, as judged by the absence of a kinetic isotope effect. The measured ratios of the preexponential factors for desorption relative to reaction of 21±2 and 47±4 for c-C4H8 and c-C4D8 respectively, are in the expected range considering the greater entropy gain associated with the transition state for desorption relative to the transition state for C–C bond cleavage. © 1999 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.477811
