
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 classicalmechanical 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 particlesolid 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 twodimensional problem is treated with a squarewell 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