TOF spectra of direct recoils. I. Chemisorption of O2, H2O, and CH2OH on magnesium

J. Albert Schultz, Moshe H. Mintz, Thomas R. Schuler, J. Wayne Rabalais

Research output: Contribution to journalArticlepeer-review

51 Scopus citations


Time-of-flight (TOF) analysis of directly recoiled surface atoms (neutrals and ions) produced by pulsed Ar+ ion irradiation has been used to monitor chemisorption of O2, H2O, and CH3OH on polycrystalline magnesium. The intensities of the H, C, O, and Mg direct recoils are obtained as a function of gas exposure dose. The reaction with O2 is fast, with saturation occurring at ∼ 10 L (1 L = 10-6 Torr s), and following either a one- or a two-site adsorption model while the H2O and CH3OH reaction are slower, with saturation occurring at ∼ 20 L, and following a nucleation and growth expression. The hydrogen direct recoil intensitiy has been calibrated to the amount of hydrogen on a methoxylated surface. This calibration allows determination of H coverages during the O2 and H2O reactions and shows a surface stoichiometry consistent with Mg(OH)2 for the water reaction. The analysis indicates that the oxygen forms an oxide at sites that are within the outermost Mg layer while the H2O and CH3OH form hydroxide and methoxide layers which are above the outermost Mg layer. Scattering and direct recoil cross-sections and shadow cones are calculated by means of a program which uses the Molière approximation to the interaction potential for single binary encounters.

Original languageEnglish
Pages (from-to)438-456
Number of pages19
JournalSurface Science
Issue number2-3
StatePublished - 1 Nov 1984
Externally publishedYes

ASJC Scopus subject areas

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


Dive into the research topics of 'TOF spectra of direct recoils. I. Chemisorption of O2, H2O, and CH2OH on magnesium'. Together they form a unique fingerprint.

Cite this