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Title:Nuclear magnetic resonance studies of simple molecules on metal surfaces
Author(s):Klug, Christopher Aaron
Doctoral Committee Chair(s):Slichter, C.P.
Department / Program:Physics, Condensed Matter
Discipline:Physics, Condensed Matter
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Physics, Condensed Matter
Abstract:We have used NMR to study the structure and reactions of acetylene and ethylene adsorbed on small catalyst particles. By monitoring $\sp{13}$C-$\sp{13}$C and $\sp{13}$C-$\sp1$H dipolar couplings we found the carbon-carbon bond length to be 1.44 $\pm$ 0.02A for acetylene adsorbed on Rh clusters at room temperature and the surface species to consist mostly of CCH$\sb2$ with a small amount of CCH. Using $\sp2$H NMR we studied the conversion of ethylene adsorbed at low temperatures on Pt clusters to the stable room temperature species (CCH$\sb3$) and also the hydrogen-deuterium exchange in this CCH$\sb3$ species. We found an activation energy of 15.2 $\pm$ 2.0 kcal/mole and preexponential factor of 10$\sp{7{\pm}1.7}$ sec$\sp{-1}$ for the conversion reaction and an activation energy of 14.3 $\pm$ 2.5 kcal/mole and preexponential factor of 4 $\times$ 10$\sp{7{\pm}2}$ sec$\sp{-1}$ for the exchange reaction. We compare these results with those obtained by other researchers. We also studied the formation of CCH$\sb3$ from the stable room temperature species of acetylene adsorbed on Pt (CCH$\sb2$) and found an activation energy of 9.3 $\pm$ 2.5 kcal/mole and a preexponential factor of 10$\sp{3{\pm}2}$ sec$\sp{-1}$torr$\sp{-1}$. In addition, we used measurements of $\sp{13}$C-$\sp1$H dipolar couplings to monitor the hydrogen population for the surface species formed from acetylene adsorbed on Pt and Ir. We were able to show that the CCH$\sb2$ species do not lose hydrogen prior to carbon-carbon bond scission on Ir but that there is a gradual dehydrogenation below the temperature of carbon-carbon bond scission for CCH$\sb2$ species on Pt.
Issue Date:1990
Rights Information:Copyright 1990 Klug, Christopher Aaron
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9114301
OCLC Identifier:(UMI)AAI9114301

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