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Dynamics of trapped spherical particles

We are in this project studying the collective behavior of two liquid droplets trapped in an optical levitator. The image below shows how two trapped glycerol droplets orbit in the potential well created by a focused laser beam. The underlying physical laws that govern the motion of each individual particle is simple but the emergent dynamics of the collection of particles is very complex. The dielectric microsphere are influenced by a constant gravitational field and an upward-pointing intense laser field. The presence of these two opposing force fields causes the system to exhibit a range of interesting behaviors, from quasi-stationary state to chaotic motion. The figure shows two particles in the oscillatory regime, when gravity is balanced by light, where the particles move in orbits.

Fluorescence of trapped spherical particles

We investigate singlet oxygen in trapped droplets using laser induced fluorescence spectroscopy. Singlet oxygen is a strong radical that violently reacts with other molecules making it extremely dangerous for any form of molecules - whether biological or atmospheric. It can be produce via excitation energy transfer by solar light absorbing chromophores such as Polycyclic Aromatic Hydrocarbons (PAHs). It is well known that anthropological pollutants contain considerable amount of PAHs that are distributed throughout in the atmosphere.
The aim of the experiments is to gain the experience and knowledge needed to design a system for high-altitude balloon experiments, where the roles played by singlet oxygen and PAHs can be investigated systematically. We will address important questions in atmospheric sciences such as the role of anthropogenic PAHs in clouds by photochemical modifications involving oxygen molecules. This project is conducted in collaboration with Dr. Murthy Gudipati at Jet Propulsion Laboratory in the USA.

Page Manager: Måns Henningson|Last update: 2/28/2019
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