Accession Number : AD0665290

Title :   ACOUSTICAL ACTIVITY AND OTHER FIRST ORDER SPATIAL DISPERSION EFFECTS IN CRYSTALS.

Descriptive Note : Technical rept.,

Corporate Author : PENNSYLVANIA UNIV PHILADELPHIA DEPT OF PHYSICS

Personal Author(s) : Portigal,D. L. ; Burstein,E.

Report Date : DEC 1967

Pagination or Media Count : 27

Abstract : It is demonstrated phenomenologically that, as a result of first order spatial dispersion, an 'acoustic activity' of transverse acoustic waves, the analog of optical activity, arises in certain crystal classes. Crystals which are optically active are also found to be acoustically active. Furthermore, in the case of propagation along high symmetry axes, the effect manifests itself, as in the case of optical activity, as a simple rotation of the plane of polarization of transverse acoustic waves. Acoustic effects of first order spatial dispersion which have no optical analog are also treated. Acoustical activity can also be inferred from the transformation properties of the acoustic phonons, and the acoustical activity of crystals may, thereby, be derived from phonon dispersion curves. An estimate of the magnitude of the acoustical activity of tellurium is so obtained. The effects of first order spatial dispersion on transverse optical phonons and the optical properties which arise from them are also considered. Practical problems involved in the observation of acoustical activity are discussed. (Author)

Descriptors :   (*CRYSTALS, ACOUSTIC PROPERTIES), (*TELLURIUM, *PHONONS), CRYSTAL LATTICES, MOLECULAR ROTATION, POLARIZATION, SYMMETRY(CRYSTALLOGRAPHY), ELASTIC PROPERTIES

Subject Categories : Acoustics
      Crystallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE