Interactions of molecules with surfaces

Technical Report · Mon Jan 01 04:00:00 EST 1990

DOI:https://doi.org/10.2172/5147852· OSTI ID:5147852

Greene, E F

This is a report of the progress made on four projects supported by DOE Grant FG02-85ER13441 in the period 1 February 1989 to 31 December 1989. (1) A long term study of the rate of transfer of electrons between gas atoms and the surfaces of crystals, using the technique of surface ionization, reached a point where it could be submitted for publication. Measurement of the energy dependence of the yields of Na{sup +}, K{sup +}, and Cs{sup +} ions formed when beams of the corresponding alkali atoms M hit a Si(111) surface and of Na{sup +} for Na striking a Pt surface at a temperature T are those expected for equilibrium for thermal kinetic energies of the incident atoms. (2) Energy transfer to surfaces has been studied by measuring the temperature rises of thermocouple surfaces exposed to molecular beams. For example, a platinum surface initially at room temperature intercepts intense molecular beams of He, Ar, H{sub 2}, N{sub 2}, and SF{sub 6} emerging from a nozzle also at room temperature. (3) He diffraction has been used to follow structural phase transitions on the (111) and (100) surfaces of Si and Ge. The seventh-order peaks of the Si(111)-7{times}7 reconstructed surface observed at room temperature first decrease with increasing temperature and then disappear near 1140 K where there are also a sharp decrease in the specular intensity and an increase in the diffuse scattering. (4) Work is in progress to measure the effect of adsorbed atoms on the forces parallel to the surface of a crystal as they are revealed by changes in the curvature of the surface. The first experiments are being done with alkali atoms adsorbed on a Si(111) surface. As others have shown, the opposite process of producing changes in the surface by bending the crystal can be observed.

• Research Organization: Brown Univ., Providence, RI (USA). Dept. of Chemistry
• Sponsoring Organization: DOE/ER
• DOE Contract Number: FG02-85ER13441
• OSTI ID: 5147852
• Report Number(s): DOE/ER/13441-12; COO--4974-12; ON: DE90005337
• Country of Publication: United States
• Language: English

Related Subjects

656003* -- Condensed Matter Physics-- Interactions between Beams & Condensed Matter-- (1987-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALKALI METALS
ATOM COLLISIONS
ATOM-MOLECULE COLLISIONS
BEAMS
COHERENT SCATTERING
COLLISIONS
DIFFRACTION
DOCUMENT TYPES
ELEMENTS
FLUIDS
GASES
HELIUM
IONIZATION
METALS
MOLECULAR BEAMS
MOLECULE COLLISIONS
NONMETALS
PROGRESS REPORT
RARE GASES
SCATTERING
SEMIMETALS
SILICON
SURFACES