Research will be conducted to extend and develop the theory of scattering of small mass particles by surfaces, with emphasis on interactions in which many quanta of energy are exchanged during the collision. A fundamental and quantum mechanical approach will be used initially, and then the theory will be extended to semiclassical limits at various levels in order to investigate the transition from the quantum mechanical to the classical regime. Initial results indicate that the diffusely scattered intensity, due to multiple phonon interactions is insensitive to fine details in the phonon density of states, and this will be further investigated for realistic surface models. This lack of sensitivity in the phonon spectra implies that the multiphonon contribution to the intensity will give directly the form factor, or transition matrix, for the atom-surface interaction potential. Analysis of available data will give the form factor as a function of exchanged energy and momentum, which will in turn lead to a determination of better models of the interaction potential. The data analysis will involve visits and some collaboration with the major experimental groups in the area of helium-surface scattering. The work will lead to applications in other related areas of gas- surface interactions including calculation of accommodation coefficients, sticking and desorption, electron-hole pair creation during collisions and scattering from disorder. %%% Theoretical research will be done on the interaction of small particles scattering from surfaces in which there are many exchanges of quantized energy and momentum. These calculations will lead to more accurate determinations of the forces which exist between the impinging particles and the surface and will develop a powerful formalism to deal. The work will be closely correlated with various experimental groups.

Agency
National Science Foundation (NSF)
Institute
Division of Materials Research (DMR)
Application #
9114015
Program Officer
G. Bruce Taggart
Project Start
Project End
Budget Start
1991-12-15
Budget End
1995-05-31
Support Year
Fiscal Year
1991
Total Cost
$144,000
Indirect Cost
Name
Clemson University
Department
Type
DUNS #
City
Clemson
State
SC
Country
United States
Zip Code
29634