Direct Spectroscopic Quantification of the Absorption & Scattering Properties for Single Aerosol

Title: Direct Spectroscopic Quantification of the Absorption and Scattering Properties for Single Aerosol Particles

Student Chapter Host: Tahsina Alam, University of Illinois, Urbana-Champaign

Abstract: Single particle cavity ring-down spectroscopy (CRDS) allows direct and continuous measurements of the extinction cross-sections for levitated micron-scale aerosol particles of constant or evolving composition. Our recent interests have concerned single particle CRDS measurements for light-absorbing particles. These measurements are made on single, spherical particles that are evolving in particle size while levitated using an optical or electrodynamic trap. Concurrently, the size of the levitated particles is quantified using elastic light scattering. This talk will summarise the important optical and physicochemical properties of aerosol particles that govern how they interact with light, discuss various methods for levitating aerosol particles, and the factors the affect the accuracy and precision with which optical properties may be assessed using our measurement platform. The limitations of the technique, and potential application in answering key questions in aerosol science, will be discussed.

About the Speaker: Michael completed his MSci degree in Chemical Physics (2012) and Ph.D. in Physical Chemistry (2016) at the University of Bristol. After postdoctoral research with Prof Jim Haywood (2016-2019) at the University of Exeter and the UK Met Office, he started his own group as a NERC Independent Research Fellow at the University of Bristol (2019-2023). Since September 2023, Michael joined the Department of Chemistry at the University of Oxford as an Associate Professor. His research is focussed on the development of new approaches to the optical spectroscopy of aerosol particles and the use of these measurements to develop better models of aerosol microphysics and chemistry.