電子線トモグラフィによるエアロゾル粒子の3次元形態解析

抄録

Aerosol particles in the atmosphere influence global climate by changing the radiative budget, i.e., they scatter and absorb sunlight. The magnitude of their scattering and absorption depends on the amount, sizes, compositions, mixing state, and shapes of particles. The effects of particle shape on their optical properties are difficult to estimate since the techniques to quantify and evaluate the shape of tiny particles are limited. In this report, electron tomography technique, which can show the three-dimensional (3D) particle shape, is reviewed. Electron tomography makes 3D digital data of materials smaller than ~1 micrometer from a series of transmission electron microscopy (TEM) images. Instead of measuring particle height, electron tomography obtains the 3D information from the tilting angles of material of interest. Such 3D digital data can be used to evaluate its optical properties using discrete-dipole approximation (DDA). The technique has been used for soot particles, which commonly have complicated structures that influence their optical properties. Measurements of 3D shape and optical properties of aerosol particles using electron tomography and DDA improve the estimation of their optical properties and evaluation of their climate effects.