The reactions of CO, NO, and oxygen on platinum surfaces have received a great deal of research attention, because of both their industrial importance in the three-way automobile catalytic converter and the academic interest surrounding the kinetic oscillations observed under some conditions. Crucial parameters in many of the kinetic models of these systems are the coverage-dependent heats of adsorption of the reacting species, which, with the exception of isosteric data for CO, have not previously been determined experimentally.Here the results of microcalorimetric measurements of the heats of adsorption of CO, NO, and O 2 as a function of coverage on Pt{110} are presented. The initial adsorption heats are 183, 160, and 335 kJ mol -1 , respectively.

The calorimetric heat of interaction for a hydrocarbon on a single-crystal surface is reported for the first time. For ethylene on Pt[110)-(1 && 2) at low coverages it is about 205 kJ/mol and drops in several steps to 120 kJ/mol with increasing coverage. Three stable species are identified on the surface, and the average bond dissociation energy of a Pt-C single bond is extracted for each. The mean value is about 223 kJ/mol, and we observe a systematic decrease from 235 to 214 kJ/mol as the number of single Pt-C bonds per adsorbate molecule increases from 2 to 4.

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Angular distributions of several photoelectron and Auger transitions have been measured above a Cu(001) single crystal at 16 different kinetic energies between 60 and 1740 eV. The results are presented as 2m full-solid-angle intensity maps -diffractograms -that permit a clear representation of the relative importance of various scattering processes at each energy and the evolution of intensity patterns with energy. The experiments are compared with single-scattering-cluster (SSC) simulations performed at corresponding energies. This serves to probe the accuracy of the SSC formalism over a vast energy and angular range and to illustrate the role of the angular momentum of the final state, polarization effects, and temperature effects. Rather good agreement is found for positions of angular patterns down to very low energies, with problems mainly in relative intensities. The sensitivity of low-energy diffraction patterns to bond lengths is demonstrated.