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Studies of Molecular Bonding, Interactions and Decomposition Reactions on the (001) Surface of Ruthenium


Toby, Brian H. (1987) Studies of Molecular Bonding, Interactions and Decomposition Reactions on the (001) Surface of Ruthenium. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/R50B-J328.


The interactions of N2, formic acid and acetone on the Ru(001) surface are studied using thermal desorption mass spectrometry (TDMS), electron energy loss spectroscopy (EELS), and computer modeling.

Low energy electron diffraction (LEED), EELS and TDMS were used to study chemisorption of N2 on Ru(001). Adsorption at 75 K produces two desorption states. Adsorption at 95 K fills only the higher energy desorption state and produces a (√3 x √3)R30° LEED pattern. EEL spectra indicate both desorption states are populated by N2 molecules bonded "on-top" of Ru atoms.

Monte Carlo simulation results are presented on Ru(001) using a kinetic lattice gas model with precursor mediated adsorption, desorption and migration. The model gives good agreement with experimental data. The island growth rate was computed using the same model and is well fit by R(t)m - R(t0)m = At, with m approximately 8. The island size was determined from the width of the superlattice diffraction feature.

The techniques, algorithms and computer programs used for simulations are documented. Coordinate schemes for indexing sites on a 2-D hexagonal lattice, programs for simulation of adsorption and desorption, techniques for analysis of ordering, and computer graphics routines are discussed.

The adsorption of formic acid on Ru(001) has been studied by EELS and TDMS. Large exposures produce a molecular multilayer species. A monodentate formate, bidentate formate, and a hydroxyl species are stable intermediates in formic acid decomposition. The monodentate formate species is converted to the bidentate species by heating. Formic acid decomposition products are CO2, CO, H2, H2O and oxygen adatoms. The ratio of desorbed CO with respect to CO2 increases both with slower heating rates and with lower coverages.

The existence of two different forms of adsorbed acetone, side-on, bonded through the oxygen and acyl carbon, and end-on, bonded through the oxygen, have been verified by EELS. On Pt(111), only the end-on species is observed. On dean Ru(001) and p(2 x 2)O precovered Ru(001), both forms coexist. The side-on species is dominant on clean Ru(001), while O stabilizes the end-on form. The end-on form desorbs molecularly. Bonding geometry stability is explained by surface Lewis acidity and by comparison to organometallic coordination complexes.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Chemistry
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemistry
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Weinberg, William Henry
Thesis Committee:
  • Gray, Harry B. (chair)
  • Weinberg, William Henry
  • Kuppermann, Aron
  • Marsh, Richard Edward
Defense Date:2 October 1986
Non-Caltech Author Email:toby (AT)
Record Number:CaltechTHESIS:02122014-142619432
Persistent URL:
Related URLs:
URLURL TypeDescription adapted for Chapter 2. adapted for Appendix A. adapted for Chapter 5. adapted for Chapter 6. adapted for Chapter 8. adapted for Appendix D. adapted for Appendix E.
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:8072
Deposited By: Benjamin Perez
Deposited On:12 Feb 2014 23:00
Last Modified:21 Dec 2019 02:18

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