Refractive Index Of Aerosol Inverted From Scattering Light With ATOFMS

Aerosol is a mixture of fine solid particles or liquid droplets suspending in air or other gases. The physical and chemical properties of aerosols, such as shape, size, density and composition, are essential parameters to be utilized to investigate the influences of aerosols on the environment, climate and health. In the past decades, a lot of methods and setups have been developed to measure the physical and chemical parameters of aerosols.Refractive index is an important parameter of atmospheric aerosol particles, whose real part relates to the light scattering properties of particles. For the particles with different chemical compositions, their refractive indexes are different. In this thesis, a new method to measure aerosols’ refractive indexes with the intensity of scattering light obtained with a home-made aerosol time-of-flight mass spectrometer (ATOFMS) has been introduced. The formulas including the relationships between the refractive index of aerosol, the geometry of the real scattering area, the intensity of scattering light and other parameters are deduced with the Mie theory. Then the refractive parameters can be deduced from the formulas and the intensity of scattering light acquired in experiments. The aerosol particles of oleic acid and sodium chloride have been selected as examples and their scattering experiments have been performed with the ATOFMS. The values of the refractive indexes of oleic acid and sodium chloride measured in our experiments agree well with the literature data, which indicates that the method can be utilized to measure other aerosols with unknown refractive indexes.A data processing software including a graphical user interface (GUI) to calculate the intensity of the scattering light, the scattering coefficient, the absorption coefficient and the extinction coefficient of aerosol has been developed with the Matlab software, improving the data processing speed and convenience efficiently.