Utilization of elastic scattering of light for characterization of single aerosol microparticles

Full text: The effect on climate due to aerosols - small, airborne particles varying in composition, size and shape - is characterized by an uncertainty resulting also from lack of information regarding their impact on radiative forcing. Recent findings show that most of the impact on radiative forcing occurs at visible wavelengths. That is why we utilize the elastic light scattering for a real-time assessment of refractive index and size of single microparticles. Resulting from the intrinsic nature of elastic light scattering from aerosol particles the non-monotonic size dependence of the scattered light intensity and its variability with changing refractive index of particles influences the function of most conventional particle spectrometers. In order to tackle the problem we propose to employ two illumination laser sources with different wavelengths and four detectors collecting the scattered light in given angular ranges. By making reasonable assumptions regarding the range of particle sizes and of complex refractive indices it will be shown that a unique particle sizing and also an unambiguous determination of the complex refractive indices of measured particles is possible opening new opportunities for single optical particle measurement. (author)