中国物理B ›› 2016, Vol. 25 ›› Issue (3): 34201-034201.doi: 10.1088/1674-1056/25/3/034201

• ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS • 上一篇    下一篇

Theoretical studies on particle shape classification based on simultaneous small forward angle light scattering and aerodynamic sizing

Jin-Bi Zhang(张金碧), Lei Ding(丁蕾), Ying-Ping Wang(王颖萍), Li Zhang(张莉), Jin-Lei Wu(吴金雷), Hai-Yang Zheng(郑海洋), Li Fang(方黎)   

  1. 1. Laboratory of Environmental Spectroscopy, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China;
    2. University of Chinese Academy of Sciences, Beijing 100049, China
  • 收稿日期:2015-06-19 修回日期:2015-09-30 出版日期:2016-03-05 发布日期:2016-03-05
  • 通讯作者: Jin-Bi Zhang E-mail:postgraduatezjb@126.com
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant No. 41275132).

Theoretical studies on particle shape classification based on simultaneous small forward angle light scattering and aerodynamic sizing

Jin-Bi Zhang(张金碧)1,2, Lei Ding(丁蕾)1, Ying-Ping Wang(王颖萍)1, Li Zhang(张莉)1,2, Jin-Lei Wu(吴金雷)1,2, Hai-Yang Zheng(郑海洋)1, Li Fang(方黎)1   

  1. 1. Laboratory of Environmental Spectroscopy, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China;
    2. University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2015-06-19 Revised:2015-09-30 Online:2016-03-05 Published:2016-03-05
  • Contact: Jin-Bi Zhang E-mail:postgraduatezjb@126.com
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant No. 41275132).

摘要: 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.

关键词: particle shape, aspect ratio, asymmetry factor, light scattering

Abstract: 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.

Key words: particle shape, aspect ratio, asymmetry factor, light scattering

中图分类号:  (Diffraction and scattering)

  • 42.25.Fx
42.68.Mj (Scattering, polarization) 92.60.Mt (Particles and aerosols)