Interactions of molecules with surfaces. Progress report, 1 February 1983-31 January 1984

Technical Report · Sun Jan 01 04:00:00 EST 1984

OSTI ID:5377231

Greene, E F

Measurements of the rate of desorption of alkali atoms from the surfaces of Si crystals reveal surface phase transitions, a well known one for the (111) face at 1020 +- 40 K and a previously unreported one for Si(100) at 980 +- 20 K. The kinetics of the desorption can be interpreted with a model that has a relatively smooth surface above the transition and a less uniform one below. The latter has special sites, such as edges, where the atoms are bound more strongly than they are at the terraces between the edges. Tetramethyldioxetane molecules seeded into an excess of hydrogen in a nozzle beam can be caused to decompose to two acetone molecules by their impact on a surface. The reaction is followed by detecting blue light emitted by electronically excited acetone formed in the collision. The light increases approximately as the cube of the excess of the kinetic energy over a reaction threshold of 50 +- 10 kJ mol/sup -1/. The amount of light varies with the nature of the surface and its temperature. On the eight surfaces tested it is largest for a polymer of perfluorinated ethylene and propylene. A simple model is proposed to account for the compensation effect that is observed when desorption occurs from surfaces that undergo a phase transition. Measurements are reported of the angular distribution of beams of He and Ar diffracted from crystals of LiF.

• Research Organization: Brown Univ., Providence, RI (USA)
• DOE Contract Number: AC02-78ER04974
• OSTI ID: 5377231
• Report Number(s): DOE/ER/04974-T3; ON: DE84006313
• Country of Publication: United States
• Language: English

Related Subjects

640301* -- Atomic
Molecular & Chemical Physics-- Beams & their Reactions
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ACETONE
ALKALI METAL COMPOUNDS
ALKALI METALS
ANGULAR DISTRIBUTION
ARGON
ATOM COLLISIONS
BEAMS
COLLISIONS
CRYSTAL STRUCTURE
CRYSTAL-PHASE TRANSFORMATIONS
DESORPTION
DISTRIBUTION
ELEMENTS
EMISSION
FLUIDS
FLUORIDES
FLUORINE COMPOUNDS
GASES
HALIDES
HALOGEN COMPOUNDS
HELIUM
KETONES
LITHIUM COMPOUNDS
LITHIUM FLUORIDES
LITHIUM HALIDES
METALS
MOLECULAR BEAMS
MOLECULE COLLISIONS
NONMETALS
ORGANIC COMPOUNDS
PHASE TRANSFORMATIONS
PHOTOEMISSION
RARE GASES
SECONDARY EMISSION
SEMIMETALS
SILICON
SURFACES