Influence of spheroidal particle shape on particle size characterization by multi-wavelength light extinction method

In order to improve the applicability, spheroidal particles are substituted for the spherical particles in the traditional modeling of multi-wavelength light extinction method. The extinction coefficient and extinction spectrum are calculated at different axial ratios under the configuration of the generalized Lorenz-Mie theory. Combining extinction spectrum with regularization inversion algorithm, the influence of particle shape on particle size characterization by multi-wavelength light extinction method is discussed in detail. That is, the arithmetic statistical average and stochastic incidence statistics are employed simultaneously to calculate the extinction spectrum in the visible light range and carry out a validation for submicron particles with a refractive index of 1.33. The corresponding comparison between inversed particle sizes and those of spherical particles yields the resulting inversion deviation within 10% for mono-sized spheroids and 20% for a polydisperse particle system with an axial ratio less than 3, but then the relative deviation may increase significantly with the axial ratio, even up to 50%. It can be seen that for particles of equivalent volume, the spheroidal shape exerts a great influence on particle size characterization, and the assumption of spheroidal particle would become crucial in the cases of axial ratio above 3.