Low-frequency dynamics of CO/Cu breakdown of Born--Oppenheimer approximation

Journal Article · Fri Jul 01 00:00:00 EDT 1994 · Journal of Vacuum Science and Technology, A (Vacuum, Surfaces and Films); (United States)

DOI:https://doi.org/10.1116/1.579120· OSTI ID:7084995

Hirschmugl, C J ^[1]; Chabal, Y J ^[2]; Hoffmann, F M ^[3]; Williams, G P ^[4]

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1. Yale University, New Haven, Connecticut 06520 (United States) NSLS, Brookhaven National Laboratory, Upton, New York 11973 (United States)
2. AT T Bell Labs, Murray Hill, New Jersey 07974 (United States)
3. EXXON Research and Engineering, Annandale, New Jersey 08801 (United States)
4. NSLS, Brookhaven National Laboratory, Upton, New York 11973 (United States)

Synchrotron infrared studies of adsorbates on surfaces offer the possibility of probing low-frequency vibrational modes and dynamics at high resolution (1 cm[sup [minus]1], 125 [mu]eV). Extensive experiments have been performed for ordered submonolayers of CO on low index Cu surfaces [([radical]3[times][radical]3)[ital R]30[degree] CO/Cu(111), [ital c](2[times]2) CO/Cu(100) and (1[times]2) CO/Cu(110)], in the 100--2500 cm[sup [minus]1] ([similar to]12.5--312.5 meV) range. These are the first IR experiments to directly probe the adsorbate-substrate vibrations for this system. In addition, however, several surprising features are observed including the dipole-forbidden hindered rotation and an unexpected broadband absorption. Two theories have been motivated by this work, and will be compared to our experimental results. The first theory is a cluster calculation by Tully, Gomez, and Head-Gordon, which takes into account the breakdown of the Born--Oppenheimer approximation and predicts lifetimes and frequencies of the vibrational modes for CO/Cu(100). Another Drude-based theory, proposed by Persson, considers the coupling of the conduction electron current to the vibrations of the adsorbates, accounting for the observation of both the broadband absorption and dipole-forbidden peak.

• DOE Contract Number: AC02-76CH00016
• OSTI ID: 7084995
• Journal Information: Journal of Vacuum Science and Technology, A (Vacuum, Surfaces and Films); (United States), Vol. 12:4; ISSN 0734-2101
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CARBON MONOXIDE
ADSORPTION
COPPER
SORPTIVE PROPERTIES
ABSORPTION SPECTRA
BORN-OPPENHEIMER APPROXIMATION
INFRARED RADIATION
SYNCHROTRON RADIATION
VIBRATIONAL STATES
BREMSSTRAHLUNG
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
ELECTROMAGNETIC RADIATION
ELEMENTS
ENERGY LEVELS
EXCITED STATES
METALS
OXIDES
OXYGEN COMPOUNDS
RADIATIONS
SORPTION
SPECTRA
SURFACE PROPERTIES
TRANSITION ELEMENTS
360606* - Other Materials- Physical Properties- (1992-)