Theoretical studies on particle shape classification based on simultaneous small forward angle light scattering and aerodynamic sizing
Autor: | Li Fang, Jin-Bi Zhang, Haiyang Zheng, Ying-Ping Wang, Jin-Lei Wu, Li Zhang, Lei Ding |
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Rok vydání: | 2016 |
Předmět: |
Physics
010504 meteorology & atmospheric sciences business.industry Forward scatter media_common.quotation_subject General Physics and Astronomy Discrete dipole approximation 01 natural sciences Ray Aspect ratio (image) Asymmetry Light scattering Optics 0103 physical sciences Perpendicular 010306 general physics business Refractive index 0105 earth and related environmental sciences media_common |
Zdroj: | Chinese Physics B. 25:034201 |
ISSN: | 1674-1056 |
Popis: | Particle shape contributes to understanding the physical and chemical processes of the atmosphere and better ascertaining the origins and chemical compositions of the particles. The particle shape can be classified by the aspect ratio, which can be estimated through the asymmetry factor measured with angularly resolved light scattering. An experimental method of obtaining the asymmetry factor based on simultaneous small forward angle light scattering and aerodynamic size measurements is described briefly. The near forward scattering intensity signals of three detectors in the azimuthal angles at 120° offset are calculated using the methods of T-matrix and discrete dipole approximation. Prolate spheroid particles with different aspect ratios are used as the shape models with the assumption that the symmetry axis is parallel to the flow axis and perpendicular to the incident light. The relations between the asymmetry factor and the optical size and aerodynamic size at various equivalent sizes, refractive indices, and mass densities are discussed in this paper. The numerically calculated results indicate that an elongated particle may be classified at diameter larger than 1.0 μm, and may not be distinguished from a sphere at diameter less than 0.5 μm. It is estimated that the lowest detected aspect ratio is around 1.5:1 in consideration of the experimental errors. |
Databáze: | OpenAIRE |
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