Kinetic and geometric isotope effects originating from different adsorption potential energy surfaces: cyclohexane on Rh(111).
Novel isotope effects were observed in desorption kinetics and adsorption geometry of cyclohexane on Rh(111) by the use of infrared reflection absorption spectroscopy, temperature programmed desorption, photoelectron spectroscopy, and spot-profile-analysis low energy electron diffraction. The desorption energy of deuterated cyclohexane (C(6)D(12)) is lower than that of C(6)H(12). In addition, the work function change by adsorbed C(6)D(12) is smaller than that by adsorbed C(6)H(12). These results indicate that C(6)D(12) has a shallower adsorption potential than C(6)H(12) (vertical geometric isotope effect). The lateral geometric isotope effect was also observed in the two-dimensional cyclohexane superstructures as a result of the different repulsive interaction between interfacial dipoles. The observed isotope effects should be ascribed to the quantum nature of hydrogen involved in the C-H···metal interaction.
The Institute for Solid State Physics, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, Chiba 277-8581, Japan.
Takanori
T
Koitaya
Sumera
S
Shimizu
Kozo
K
Mukai
Shinya
S
Yoshimoto
Jun
J
Yoshinobu
D000327:Adsorption; D003510:Cyclohexanes / Q000737:chemistry*; D007554:Isotopes / Q000737:chemistry; D007700:Kinetics; D011789:Quantum Theory; D012238:Rhodium / Q000737:chemistry*; D013499:Surface Properties
D003510:Cyclohexanes; D007554:Isotopes; C506365:Cyclohexane; D012238:Rhodium