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Helium atom diffraction from clean and krypton film-covered graphite surfaces

Thesis/Dissertation ·
OSTI ID:6913277
Helium atom scattering was used to study the basal plane of graphite and the commensurate-incommensurate transition of monolayer krypton films adsorbed on graphite. A 17-meV energy beam was used in both works. Bound state energies of /sup 4/He atoms physisorbed on graphite (0001) surfaces were re-determined with improved resolution and precision. The energy levels were all slightly deeper than was previously thought, and an additional high-lying level was resolved. These results were in good agreement with recent theoretical calculations. The commensurate-incommensurate transition of monolayer krypton films on graphite was observed for transition temperature in the range 50.5 to 60 K. The change in lattice spacing appears continuous. The slightly incommensurate phase was disordered but still apparently solid. A possible precursor of the transition was observed as a decrease of specular and diffracted beam intensities while the film was still commensurate. The rotational transition of the incommensurate Kr monolayer was also observed. Results were in qualitative agreement with Shiba's predictions. In the theoretical work the potential energy of a He atom above an ordered overlayer of Kr, Xe, or Ar on either a graphite or a Ag surface was calculated.
Research Organization:
Pennsylvania State Univ., University Park (USA)
OSTI ID:
6913277
Country of Publication:
United States
Language:
English

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Related Subjects

640301* -- Atomic
Molecular & Chemical Physics-- Beams & their Reactions
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ADSORPTION
ATOM COLLISIONS
CARBON
COLLISIONS
ELEMENTAL MINERALS
ELEMENTS
ENERGY LEVELS
ENERGY RANGE
EV RANGE
EVEN-EVEN NUCLEI
FILMS
FLUIDS
GASES
GRAPHITE
HELIUM
HELIUM 4
HELIUM ISOTOPES
ISOTOPES
LIGHT NUCLEI
METALS
MILLI EV RANGE
MINERALS
NONMETALS
NUCLEI
RARE GASES
SILVER
SORPTION
STABLE ISOTOPES
SURFACES
THIN FILMS
TRANSITION ELEMENTS
VERY LOW TEMPERATURE