Accession Number : AD0618826

Title :   ON THE TOTAL FORCE OF ELASTIC SCATTERING. NEUTRAL PARTICLES AND PERFECT CRYSTAL,

Corporate Author : UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES ENGINEERING CENTER

Personal Author(s) : Beder,E.

Report Date : 09 SEP 1963

Pagination or Media Count : 39

Abstract : Quantum and classical-mechanical microscopic theories are developed for the total force on a cold solid plane surface resulting from the elastic scattering of an incident uniform cold beam of particles. The solid is a semiinfinite perfect dielectric crystal. The particles are neutral noninteracting mass points. The particle-solid interaction potential is that of physical adsorption normal to the surface, with a small sinusoidal perturbation along the surface to represent crystal nuclei. With vanishing perturbation the scattering becomes purely specular. For conceptual simplicity the two-dimensional problem is treated with a square-well interaction potential. Particle energy and incidence effects are studied. The quantummechanical forces are shown to be specular at very high energies (particle deBroglie wave length lambda approaches 0), and in a domain of low energies (lambda > d). Between these limits some points are computed for helium incident on LiF to show a domain of 'strong diffraction' or significantly nonspecular tangential forces. The quantum theory is shown to be essential in this domain and below where the classical theory fails. (Author)

Descriptors :   (*ELASTIC SCATTERING, ATOMS), (*QUANTUM THEORY, KINETIC THEORY), (*SURFACE PROPERTIES, CRYSTALS), (*FORCE(MECHANICS), ADSORPTION, DIELECTRICS, PARTICLE TRAJECTORIES, POTENTIAL THEORY, PERTURBATION THEORY

Distribution Statement : APPROVED FOR PUBLIC RELEASE