Philip J. Wyatt
Ford Motor Company
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Featured researches published by Philip J. Wyatt.
Applied Optics | 1964
Philip J. Wyatt; V. Robert Stull; Gilbert N. Plass
The infrared transmittance of water vapor has been calculated over a wide range of path lengths, pressures, and temperatures. All contributing lines whose relative intensity is greater than 10−8 times that of the strongest line in any particular band have been included in the calculation. In addition, the contributions from the four major isotopic species have been included. Although the vibrational analysis has been done exactly, the rotational contributions for some of the weaker lines have been calculated from the symmetric rotator approximation. This approximation was not used for the frequencies and intensities of the stronger lines below 3400 cm−1 which are correctly included in the calculations. The final transmittance tables have been generated using the quasi-random model of molecular band absorption.
Journal of Colloid and Interface Science | 1972
Philip J. Wyatt; David T. Phillips
Abstract The importance of light scattering for the study of small particles has long been recognized. Only recently has it become possible to measure the light-scattering characteristics of individual microparticles in their natural state. This paper describes how the Differential II achieves these measurements and the applications of the single-particle measurements that are possible using this instrument. Individual particles of diameters ranging from 100 to 5000 nm are introduced into a chamber where they are suspended and automatically held stationary in a laser beam by means of time-varying electrostatic fields. A rotating photomultiplier detector system measures the intensity of light scattered by the levitated particle as a function of scattering angle. The atmosphere within the chamber may be controlled and changes in the levitated aerosol particle may be studied over periods of many hours. In addition to smog-like aerosol particles, the Differential II has been used to study the physical properties of polystyrene latex spheres, viable and dead bacteria, and spores. Operation of the instrument is briefly described and selected measurements performed with the instrument are presented.
Applied Optics | 1980
Philip J. Wyatt
Fly ash samples from two different generating plants have been examined by laser light scattering techniques. Individual particles below approximately 3-microm diam, found to be primarily spherical, were electrostatically levitated in a single-particle light scattering photometer while their differential light scattering (DLS) patterns were recorded. During this measurement period, the relative humidity within the scattering cell could be varied to study the water accretion properties of the suspended particle. The recorded DLS patterns are used to derive the complex refractive index, size, and accreted layer thickness of the particle. Each particle appears to have a different refractive index, probably indicative of the varied microscopic conditions of formation. Even at very high relative humidities, the fly ash particle surface does not appear to have a natural affinity for water, contrary to popular expectations.
Applied Optics | 1964
V. Robert Stull; Philip J. Wyatt; Gilbert N. Plass
The infrared transmittance of carbon dioxide has been calculated over a wide range of path lengths, pressures, and temperatures from 500 to 10,000 cm−1. Values of the transmittance are given at intervals of 2.5 cm−1. In addition, transmittance values are also given which have been averaged over larger intervals. All contributing spectral lines whose relative intensity is greater than 10−8 that of the strongest line in any particular band have been included in the calculation. In addition, the contributions from the eight major isotopic species have been included. The calculation of the vibrational energy levels included terms through the third power of the vibrational quantum number and also the effects of Fermi resonance. The final transmittance tables were generated using the quasi-random model of molecular band absorption.
Journal of the Optical Society of America | 1962
Philip J. Wyatt; V. Robert Stull; Gilbert N. Plass
The quasi-random model of band absorption provides a means for the accurate representation of molecular absorption over finite frequency intervals. It does not suffer from the limitations of the Elsasser and statistical models. The spacing between actual spectral lines is not constant nor does it vary in a random manner. The essential features of the actual arrangement of these lines are reproduced in the quasi-random model by the division of the frequency interval of interest into much smaller intervals within which the lines are assumed to be arranged at random. The actual intensity distribution including the important effect of the numerous weak lines is accurately simulated. A new expression for the transmittance related to a finite frequency interval is derived. The absorption from the wings of the spectral lines in other intervals is taken into account. Through these and other features the quasi-random model provides a means of accurately representing molecular absorptance over finite frequency intervals.
Applied Optics | 1988
Philip J. Wyatt; Kevin L. Schehrer; Steven D. Phillips; Christian Jackson; Yu-Jain Chang; Randall G. Parker; David T. Phillips; Jerrold R. Bottiger
A new multiangle light scattering instrument is described for the classification of single aerosol particles in a flowing gas stream. Simultaneous measurement at sixteen scattering angles over the surface of a spherical chamber permits determination of a variety of optical observables useful for the subsequent characterization of each measured particle. Particles of 0.2 - 4.0-microm diameter have been measured and data collected at rates exceeding 200 particles/s. Data from polystyrene latex particles, liquid droplets, and irregular particles are shown. Spherical particle data are compared to theoretical calculations and used to confirm the validity of the measurement as well as a powerful calibration procedure.
Applied Optics | 1979
Harry C. H. Chen; Peter W. Barber; Philip J. Wyatt
The extended boundary condition method is used to make angular scattering calculations for a polydisperse suspension of prolate spheroidal particles. To aid in interpretation of the nonspherical results, calculations are also made for spherical particle suspensions. The basic particle models are two-layered approximations of common bacteria. Using a quasi-Gaussian size distribution, changes in the average particle size are found to have the dominant effect on the scattering of a polydisperse suspension. The spherical and prolate spheroidal two-layered results are compared with similar calculations using the Rayleigh-Gans-Debye approximation and to results based on volume-averaged homogeneous models.
Journal of Chemical Physics | 1962
V. Robert Stull; Philip J. Wyatt; Gilbert N. Plass
The vibrational energy levels of the eight most abundant isotopic species of carbon dioxide have been calculated. Over 1800 energy levels are given for each isotope. The calculations included terms to the third order in the vibrational quantum numbers and took account of the Fermi resonance. The matrices were diagonalized by an eigenvalue routine of great accuracy.
Applied Optics | 1972
David T. Phillips; Philip J. Wyatt
The use of single-particle light-scattering measurements to determine the origin of atmospheric hazes has been explored by measurement of laboratory aerosols, field samples, and computer analysis of the light-scattering data. The refractive index of measured spherical particles 800 nm to 1000 nm in diameter was determined within 2%. For particles of diameter less than 500 nm the measurement of absolute scattering intensity is required for complete analysis. Distinctive nonspherical and absorbing particles were observed both in automotive exhaust and atmospheric samples. Electrostatic suspension of atmospheric particulates is demonstrated to provide a practical approach to optical measurement of single particles. The technique may be used to calibrate optical particle counters or identify particles with unique shape or refractive index.
Applied Optics | 1982
Philip J. Wyatt
The differential light scattering (DLS) properties of six popular cola drinks are compared (three standard and three saccharine-sweetened). Each produces a unique DLS pattern characteristic of its unique taste. The probable demise of the subjective taste test in favor of a quantiative quality control DLS measurement is proposed.