Interaction of cyclobutane with the Ru(001) surface: Low-temperature molecular adsorption and dissociative chemisorption at elevated surface temperature
- Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California 93106-5080 (United States)
- Department of Chemical Engineering, Seoul National University, Shinlin-Dong, Kwanak-Ku, Seoul, (Korea) 151-742
- Department of Chemistry, University of California, Santa Barbara, Santa Barbara, California 93106-9510 (United States)
- Department of Chemical Engineering and Department of Chemistry, University of California, Santa Barbara, Santa Barbara, California 93106-9510 (United States)
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-C{sub 4}H{sub 8} and c-C{sub 4}D{sub 8} 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{sup {minus}1} (2140 cm{sup {minus}1}) which is attributed to the strong interaction of the cyclobutane C{endash}H (C{endash}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{endash}H mode. We have also measured the trapping-mediated dissociative chemisorption of both c-C{sub 4}H{sub 8} and c-C{sub 4}D{sub 8} at surface temperatures between 190 and 1200 K. The measured activation energies with respect to the bottom of the physically adsorbed well for c-C{sub 4}H{sub 8} and c-C{sub 4}D{sub 8} are 10thinsp090{plus_minus}180 and 10thinsp180{plus_minus}190 cal/mol, respectively. The trapping-mediated chemisorption of cyclobutane is believed to occur via C{endash}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{plus_minus}2 and 47{plus_minus}4 for c-C{sub 4}H{sub 8} and c-C{sub 4}D{sub 8} 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{endash}C bond cleavage. {copyright} {ital 1999 American Institute of Physics.}
- OSTI ID:
- 300141
- Journal Information:
- Journal of Chemical Physics, Vol. 110, Issue 3; Other Information: PBD: Jan 1999
- Country of Publication:
- United States
- Language:
- English
Similar Records
Trapping-mediated and multilayer-induced dissociative chemisorption of cyclobutane on Ru(001)
Isotope effects in trapping-mediated chemisorption of ethane and propane on Ir(110)