Vibrational excitation dynamics in photodesorption

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Abstract

Quantum state specific detection of photodesorbed molecules enables measuring their final state distributions in the translational and internal degrees of freedom, which contain a wealth of information about the desorption mechanism and dynamics. Vibrational state populations are of particular interest because of the information they contain about the lifetime and nature of the electronic excited states responsible for desorption. The measured vibrational distributions for nondissociative photodesorption of diatomic molecules tend to resemble Boltzmann distributions with temperatures of 600-1200 K for desorption from metal surfaces, and 1700-2000 K for semiconductors and oxides. Two-dimensional quantum dynamics calculations of the desorption process show that these vibrational distributions can be reproduced only if the intramolecular equilibrium bondlength in the electronic excited state is remarkably similar to that of the ground state. In particular, the results are inconsistent with a desorption mechanism in which the intramolecular bondlength change upon excitation is similar to that of electron capture in the gas phase.

Original languageEnglish (US)
Pages (from-to)174-185
Number of pages12
JournalSurface Science
Volume390
Issue number1-3
DOIs
Publication statusPublished - Nov 18 1997

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All Science Journal Classification (ASJC) codes

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

Keywords

  • Atomistic dynamics
  • Carbon monoxide
  • Nickel oxides
  • Nitrogen
  • Photon stimulated desorption
  • Platinum
  • Silicon
  • Vibrations of adsorbed molecules

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