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|Title:||Nuclear Magnetic Resonance Study of the Bonding of Carbon-Monoxide to Palladium and Platinum Surfaces (Nmr)|
|Author(s):||Shore, Susan Eileen|
|Department / Program:||Physics|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Subject(s):||Physics, Condensed Matter|
|Abstract:||The ('13)C and ('17)O NMR of CO chemisorbed on small particles of Pd and Pt has been observed. The ('17)O resonance represents the first reported NMR observation of a spin larger than 1/2 adsorbed on a metal surface.
At low temperatures, the ('13)C resonance of CO on Pd is centered at 540 ppm downfield from the ('13)C resonance of tetramethylsilane (TMS). The line position is interpreted as the sum of a chemical shift of 230 ppm, typical of CO in transition metal carbonyls, and a Knight shift of 310 ppm. The ('13)C lineshape and spin lattice relaxation time T(,1) were measured from 77 K to 400 K. The temperature dependence of the T(,1) is used to confirm the existence of a Knight shift. From the motional narrowing of the NMR line a diffusion energy of 6 + 2 kcal/mol for CO on the Pd surface is deduced. A C-O bond length of 1.20 + .03 A for CO chemisorbed on Pd was measured using a spin echo double resonance (SEDOR) experiment observing the ('17)O NMR.
The ('17)O NMR lineshape for CO chemisorbed on Pt shows two distinct peaks. The ('17)O spin lattice relaxation time T(,1) is similar on the two peaks. The ('13)C T(,1) measured through the ('17)O NMR in a coherence transfer experiment at each of the two peaks is also similar. SEDOR measurements of the C-O bond length for CO chemisorbed on the Pt surface indicate a bond length of 1.15 + .04 A, and possibly an additional bond length of 1.35 + .05 A.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1986.
|Date Available in IDEALS:||2015-05-13|