Light-scattering instrument for kinetic measurements in aerosols with changing particle size distributions

Abstract

The construction and use are described of a laser light-scattering instrument for kinetic measurements of the particle size distribution in a developing aerosol. In the present stage of development, the time resolution (of the order of seconds) is adequate for the study of aerosols which are developing by growth and by coagulation. Such an in situ measurement is preferable for particles, and for kinetic studies. The systems investigated are of importance in atmospheric pollution, namely, the formation of solid particles by interaction of ammonia and sulphur dioxide, and the hygroscopic growth of sulphuric acid droplets in humid atmospheres. The precision of the data-analyzing procedure is such that it yields modal particle sizes and distribution spread parameters accurate to within 4 and 10% respectively, even with about 5% random fluctuations in the measurements of the angular distribution of scattered intensity.