The coverage dependence of the pre-exponential factor for desorption

Edmund G Seebauer, A. C.F. Kong, L. D. Schmidt

Research output: Contribution to journalArticlepeer-review


The pre-exponential factor for desorption υ0 is seldom measured as other than low surface coverage θ and is typically assumed to be independent of θ. Variations in υ0 with θ are critically important in describing surface equilibrium and rate processes and in testing theories of desorption. It has often been overlooked that the functional depedence of υ0 on θ may be readily determined from thermodynamic data used to determine isosteric heats of adsorption if the sticking coefficient S(θ) is known. We present υ0(θ) values for approximately 45 adsorption species calculated from or reported in the literature for approximately adsorption systems. It is found that variations in υ0 by factors of 106 are often observed. In approximately half of these examples υ0 decreases by a factor of 103 or more and in the rest of the systems υ0 is constant or decreases by less than 103; in very few cases does υ0 increase significantly with coverage. Current theoretical models for υ0 are briefly reviewed, and it is shown that none predicts such large coverage variations. However, analysis of low coverage models suggest that adsorbate-induced changes in the surface phonon spectrum may play a critical role.

Original languageEnglish (US)
Pages (from-to)417-436
Number of pages20
JournalSurface Science
Issue number3
StatePublished - Jan 1988
Externally publishedYes

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Materials Chemistry


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