George E. Peterson

Structure and phonon spectra of SiO2, B2O3 and mixed SiO2B2O3 glasses

Abstract We present and interpret computed infrared and Raman spectra for SiO2, B2O3 and mixed SiO2B2O3 glasses. The calculations reproduce the main observed spectral bands in all three types of glass - very fully in the case of SiO2, and with a reasonable degree of success for B2O3 and SiO2B2O3. An analysis based on a network of B3O6 boroxol rings gives a satisfactory account of the optical spectra of glasses containing B2O3, whereas calculations based on a network of simple BO3 triangles do not.

Parametric effects on the bandwidth of a single-mode fiber with experimental verification.

Based on a set of exact vector form solutions to Maxwells equations for optical waveguides, we studied the parametric effects on propagation characteristics of the HE(11) mode, varying the lightguide parameters (lambda,Delta,a,alpha). In this work a three-term Sellmeier equation was employed to describe accurately the material dispersion of a single-mode fiber doped with GeO(2). The calculated results are compared with the measured values and found to be in good agreement.

A rigorous numerical solution to Maxwell's equation for lightguides

Abstract We have obtained numerical solutions to the vector form of Maxwells equation for lightguides. All six components of the electromagnetic field are obtained. Materials dispersion is included. Poynting vectors, effective indices and group indices have been calculated.

Radio frequency properties of ceramic, high-Tc superconductors

The impedance of circuits consisting of superconducting ceramic strips (typically 58 mm long, 5.4 mm wide, and 0.175 mm thick), with wires indium-soldered to them, was measured and compared with that of copper strips of the same size and with similar connections. The superconducting strips were encapsulated in glass to stop deterioration due to moisture. The circuits contained both internal and external inductance and resistance at radio frequencies. From Q measurements both the resistive and reactive components were calculated. The improvement factor for the circuit consisting of the copper strip cooled to liquid nitrogen temperature is 35% over the range from 1 MHz to 20 MHz. Comparing the circuit with the copper strip at room temperature with the superconductor at liquid nitrogen temperature the improvement factor is 63% at 1 MHz, decreasing to 56% at 20 MHz. This improvement may be worthwhile for some applications. Data were also taken at 1000 MHz and 10000 MHz. In both cases the improvement over copper was slight. These factors are quite sample-dependent but are always rather small for the ceramic material used. A theoretical discussion of the conductivity of these ceramics is included. The rationale for using indium solder is also examined.<<ETX>>

MOLECULAR STRUCTURES OF PCl4F, PCl3F2, AND PCl2F3: PURE CHLORINE NUCLEAR QUADRUPOLE RESONANCE AND LOW TEMPERATURE F19 NUCLEAR MAGNETIC RESONANCE SPECTRA

Abstract Chlorine nuclear quadrupole resonance spectra determined at 77°K. and F19 n.m.r. data obtained as a function of temperature for the molecular forms of PCl4,F, PCl3F2, and PCl2F3 were correlated with previous infrared and Raman spectra. The data support the trigonal bipyramid as the structural model for the halides with fluorine atoms showing a preference for axial positions. The symmetry of PCl4F is C3v and that of PCl3F2 is D3h. For PCl2F3 the data are best interpreted in terms of the C2v point group. Further, the data give no evidence for any significant variation in molecular structure between the gas, liquid, and solid states. Symmetry considerations and the F19 n.m.r. data support the presence of axial P[sbnd]F π-bonding. The chlorine quadrupole data indicate a lesser importance of π-bonding in the P[sbnd]Cl bonds.

RANDOM VECTOR STATISTICAL STUDIES OF AMORPHOUS MATERIALS

The lack of translational symmetry in amorphous solids restricts the amount of information obtainable from direct diffraction studies of glass structure. It also complicates the manner in which the structure can itself be conveniently and concisely described. Because of these difficulties it is necessary to apply all of the available experimental and theoretical techniques to the solution of this problem. The presence of a quadrupole moment at its nucleus allows the variation in symmetry at boron sites to be conveniently studied by nuclear magnetic resonance. This is not the case for silicon and thus an added dimension is given to structural studies of borate glasses. Although glasses in which boron is the major or only glass former are rare, it is a very important ingredient in a large number of commercial glasses. Because of this, and because of the interesting and sometimes anomalous properties shown by borate glasses, their structure continues to be of special scientific and technological interest.