Vibrational linewidths of adsorbed molecules by infrared emission spectroscopy

Technical Report · Fri Nov 01 04:00:00 EST 1985

OSTI ID:6199235

Tobin, R G

Infrared emission spectroscopy is the only experimental technique capable of high resolution vibrational studies of adsorbates on well characterized single-crystal metal surfaces in the frequency range below 1000 cm . The present work reports the first measurement of the linewidth of the C-Pt stretching vibration of CO on Pt(111), and the first detailed investigation of any molecule-substrate vibrational mode. The linewidth has been studied at sample temperatures between 275 and 400K, and the variations are found to be significantly less than predicted by theories of lifetime broadening. Based on this fact, and the observed asymmetry of the line shape, it is concluded that the linewidth is predominantly inhomogeneous. The O-Pt stretching vibration of atomic oxygen on Pt(111) has also been observed. The technique of infrared direct absorption spectroscopy was used to make an extensive study of the C=0 stretching vibration of CO on evaporated Ag, Au, and Cu films at 2K. The adsorption behavior is found to depend strongly on the deposition temperature of the film. An investigation of the shift of the C=0 frequency with CO exposure reveals both chemical and dynamic interactions between the molecules. No evidence is found for an enhancement of the infrared polarizability analogous to the Raman enhancement at 'active sites' proposed in some theories of Surface Enhanced Raman Scattering.

• Research Organization: Lawrence Berkeley Lab., CA (USA)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 6199235
• Report Number(s): LBL-20574; ON: DE86006061
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360104* -- Metals & Alloys-- Physical Properties
ABSORPTION SPECTROSCOPY
ADSORPTION
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CHALCOGENIDES
COPPER
ELEMENTS
EMISSION SPECTROSCOPY
ENERGY LEVELS
EXCITED STATES
FILMS
GOLD
INFRARED SPECTRA
METALS
NICKEL
NONMETALS
OXIDES
OXYGEN
OXYGEN COMPOUNDS
PLATINUM
PLATINUM METALS
SILVER
SORPTION
SORPTIVE PROPERTIES
SPECTRA
SPECTROSCOPY
SURFACE PROPERTIES
TRANSITION ELEMENTS
VIBRATIONAL STATES