ESR studies of surface adsorption and catalysis under ultra-high vacuum conditions. Progress report, March 1, 1980-February 29, 1981
This project is directed to developing ESR for the study of surface adsorption and catalysis on clean well-characterized metallic and oxide surfaces under ultra-high vacuum (UHV) conditions and to compare the results with real surfaces, which are important in actual catalysis. Results with ESR-UHV system on the NO/sub 2//Cu system showed that only in the presence of H/sub 2/O can the surface process(es) proceed that lead to stable Cu/sup 2 +/ complexes which are observable by ESR. By monitoring the CREMSEE (cyclotron-resonance from microwave-induced secondary electron emissions) threshold, definite evidence for the oxidation of the Cu surface by the clean NO/sub 2/ has been obtained. In real systems, as opposed to the clean surfaces prepared under UHV conditions, small amounts of H/sub 2/O are usually present. The UHV studies permitted a demonstration of the reactivity requirements. Detailed studies of the oxidation process of NO/sub 2/ on Cu have been performed. A newer ESR-UHV system with better expected performance has been built. An extensive study of motional dynamics of free radicals on supported surfaces has been completed. These include the O/sub 2//sup -/ radical absorbed on Ti supported on crushed vycor and NO/sub 2/ adsorbed on crushed vycor. The O/sub 2//sup -/ is found to exhibit planar rotation about an axis perpendicular to the internuclear axis of the O/sub 2//sup -/ and parallel to the normal to the plane. The higher temperature motion may be fit with a small activation energy of 0.5Kcal/mole, while the lower temperature motion shows anomalies. The NO/sub 2/ exhibits planar-rotation at the lower temperature, but above 77/sup 0/K it becomes more nearly isotropic presumably due to translational diffusion. Preliminary experiments imply that addition of acetylene increases the rate of rotational motion of the O/sub 2//sup -/. Preliminary studies leading to time-resolved UHV-ESR experiments of photo-induced catalysis have been performed with the new excimer laser.
- Research Organization:
- Cornell Univ., Ithaca, NY (USA). Dept. of Chemistry
- DOE Contract Number:
- AS02-78ER04991
- OSTI ID:
- 6699661
- Report Number(s):
- DOE/ER/04991-2
- Country of Publication:
- United States
- Language:
- English
Similar Records
ESR studies of surface adsorption and catalysis under ultra-high vacuum conditions. Final report
ESR studies of surface adsorption and catalysis under ultra-high vacuum conditions. Progress report, March 1, 1982-February 28, 1983
Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
COPPER
SORPTIVE PROPERTIES
NITROGEN DIOXIDE
ADSORPTION
OXYGEN
TITANIUM
CHEMISORPTION
COPPER COMPLEXES
DESIGN
ELECTRON SPIN RESONANCE
EQUIPMENT
RADICALS
TEMPERATURE DEPENDENCE
ULTRAHIGH VACUUM
VYCOR
WATER
CHALCOGENIDES
CHEMICAL REACTIONS
COMPLEXES
ELEMENTS
HYDROGEN COMPOUNDS
MAGNETIC RESONANCE
METALS
NITROGEN COMPOUNDS
NITROGEN OXIDES
NONMETALS
OXIDES
OXYGEN COMPOUNDS
RESONANCE
SEPARATION PROCESSES
SORPTION
SURFACE PROPERTIES
TRANSITION ELEMENT COMPLEXES
TRANSITION ELEMENTS
400201* - Chemical & Physicochemical Properties