Surface tension can impact the growth of atmospheric aerosol particles and is expected to influence their activation as cloud droplets and their ability to act as ice nuclei. The direct measurement of surface tension in atmospheric particles remains challenging. In this presentation we will provide an overview of a method that we have developed for measuring the surface tension of single aerosol particles through the use of a dual beam optical trap. The trap consists of two counter-propagating laser beams which trap a single particle at their common focal point. The optical stress induced at the particle surface by these counter-propagating beams causes the particle to be deformed from its previously spherical shape. The measured deformation can be used to calculate particle surface tension. Simultaneously, the optical trap can measure the complex refractive index of single particles as a result of water uptake and loss that occurs during heating and cooling. This presentation will discuss both surface tension and complex refractive index measurements that we have performed on systems that are surrogates for atmospheric aerosol particles.

Surface tension measurements of aqueous organic and inorganic aerosol particles

2019 Fall National Meeting

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