IMX Seminar Series - Chemical and physical processes in the confined environment of an aerosol particle

Photochemical processes have been identified as the main cause of the degradation and oxidation of matter in atmospheric aerosol particles. When light interacts with an aerosol particle, the light intensity inside the particle can be significantly increased as the latter acts as a light-amplifying cavity. These optical confinement effects lead to an acceleration of photochemical reactions in aerosol particles compared to reactions in extended condensed matter. We studied and quantified the acceleration of in-particle photochemistry using photoacoustic spectroscopy [1] and X-ray spectroscopic imaging of single aerosol particles [2].

The formation of new particles through condensation from the gas phase is an important source of aerosols. Volatile vapor components can accelerate the nucleation of other, less volatile vapor components by orders of magnitude. To investigate the molecular mechanism behind accelerated vapor nucleation, we developed a new nucleation tool based on Laval expansions combined with soft cluster ionization [1]. We find that a catalytic cycle involving transient heteromolecular clusters is the origin of this acceleration phenomenon.

1. J.W. Cremer, K.M. Thaler, C. Haisch, R. Signorell, „Photoacoustics of single laser-trapped nanodroplets for the direct observation of nanofocusing in aerosol photokinectics”, Nat. Commun., 7, 10941 (2016)
2. P.C. Arroyo, G. David, P.A. Alpert, E.A. Parmentier, M. Ammann and R. Signorell, „Amplification of light within aerosol particles accelerates in-particle photochemistry”, Science, 376, 293-296 (2022).
3. C. Li, J. Krohn, M. Lippe and R. Signorell, Sci. Adv., 7, eabd9954 (2021).

Bio: Ruth Signorell received her MSc and PhD degrees in molecular spectroscopy from the Swiss Federal Institute of Technology (ETH). She began her aerosol research in 2002 as an assistant professor at the Georg-August University of Göttingen. From 2005 to 2012 she was an associate professor and later a full professor at the University of British Columbia in Vancouver, Canada. In 2012 she returned to Switzerland to take up a position as full professor of physical chemistry at the Department of Chemistry and Applied Biosciences at ETH Zurich. Her research interests focus on spectroscopic studies of fundamental processes in aerosol particles and clusters held together by weak intermolecular forces. She is co-editor of a book on the topic “Fundamentals and Applications in Aerosol Spectroscopy (MUOAA)” and co-founder of the aerosol conference “Molecular-Level Understanding of Atmospheric Aerosols”.