In order to expand the possibility of better applicability, spheroid particles are adopted to replace the traditional spherical particle assumption in the modeling of multi-wavelength light extinction method. The extinction coefficient and extinction spectrum are then calculated at different axial ratios based on the generalized Mie theory. Combining extinction spectrum with regularized inversion algorithm, the effect of particle shape on particle size characterization in multi-wavelength extinction method is discussed in detail. The results show that in the visible light range, for submicron particles with a refractive index of 1.33, inversed particle sizes are compared with the sphere, which yields the equivalent volume spheroid in axial ratio of 1-3 particle size inversion error within 10%, while, when the ratio is above 3, the relative deviation may reach about 50%. It can be seen that for particles of equal volume, the spheroidal shape exerts a great influence on the particle size measurement of the multi-wavelength extinction method, and the assumption of spheroidal particle is more suitable for the cases of axial ratio within 3.
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