Accession Number : ADA132698

Title :   Low-Frequency Raman Scattering from Vitreous and Molten B2O3.

Descriptive Note : Technical rept.,

Corporate Author : HOWARD UNIV WASHINGTON DC DEPT OF CHEMISTRY

Personal Author(s) : Walrafen,G E ; Hokmabadi,M S ; Krishnan,P N ; Guha,S ; Munro,R G

PDF Url : ADA132698

Report Date : 08 Sep 1983

Pagination or Media Count : 47

Abstract : Integrated Raman intensities of bands between 0-900 per cm have been obtained for molten B203 from 288-906 C. Emphasis was placed on the highly depolarized low-frequency contour (adjoining the exciting line) which is intense, broad, skewed to high frequencies, and displays a weak, broad, shoulder centered between 100-150 per cm. The total integrated contour intensity from 0-300 as well as the peak intensity, obey the one-phonon Bose-Einstein (B.-E.) relation within 6%. The integrated intensity of the polarized 800 per cm boroxol ring (B306) line, however, decreases with temperature rise, in quantitative agreement with previous work, J. Chem. Phys., 72, 113 (1980), and correction using neutron scattering results yields a enthalpy H value of 5.0 kcal/mole ring rupture. The low-frequency contour probably involves nonsymmetric collective modes of very large assemblies, cages, or rings, as well as librations of B306 groups (100-150 per cm), and the fact that the B.-E. distribution is obeyed at temperatures for which B306 ring rupture is important indicates that such large temporal aggregates are involved that whether B03 triangles or B306 rings are present may be nearly irrelevant.

Descriptors :   *Boron oxides, *Low frequency, *Raman spectra, Intensity, Peak values, Temperature, Neutron scattering, Melting, Vitreous state

Subject Categories : Ceramics, Refractories and Glass
      Atomic and Molecular Physics and Spectroscopy

Distribution Statement : APPROVED FOR PUBLIC RELEASE