Accurate Measurement of the Optical Properties of Single Aerosol Particles Using Cavity Ring-Down Spectroscopy

Michael I Cotterell*, Jamie W Knight, Jonathan P Reid, Andrew J Orr-Ewing*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

10 Citations (Scopus)
99 Downloads (Pure)


New approaches for the sensitive and accurate quantification of aerosol optical properties are needed to improve the current understanding of the unique physical chemistry of airborne particles and to explore their roles in fields as diverse as chemical manufacturing, healthcare, and atmospheric science. We have pioneered the use of cavity ring-down spectroscopy (CRDS), with concurrent angularly resolved elastic light scattering measurements, to interrogate the optical properties of single aerosol particles levitated in optical and electrodynamic traps. This approach enables the robust quantification of optical properties such as extinction cross sections for individual particles of known size. Our measurements can now distinguish the scattering and absorption contributions to the overall light extinction, from which the real and imaginary components of the complex refractive indices can be retrieved and linked to chemical composition. In this Feature Article, we show that this innovative measurement platform enables accurate and precise optical measurements for spherical and nonspherical particles, whether nonabsorbing or absorbing at the CRDS probe wavelength. We discuss the current limitations of our approach and the key challenges in physical and atmospheric chemistry that can now be addressed by CRDS measurements for single aerosol particles levitated in controlled environments.
Original languageEnglish
Pages (from-to)2619 - 2631
Number of pages13
JournalJournal of Physical Chemistry A
Issue number17
Early online date25 Apr 2022
Publication statusPublished - 5 May 2022

Bibliographical note

Funding Information:
We are grateful to many former and current colleagues, and to visitors to the University of Bristol’s Aerosol Research Centre for their contributions to the development of single-particle CRDS methods. These include Timothy Butler, Johanna Miller, Thomas Preston, Rui Wang, Joanna Egan, Rose Willoughby, Jim Walker, Antonia Carruthers, Bernard Mason, Hongze Lin, Fenghong Chu, Antonio Valenzuela, Rachael Miles, Svemir Rudić, Allen Haddrell, and Bryan Bzdek. We thank NERC (NE/C512537/1, NE/H001972/1) for funding the development and application of this research and for the award of an Independent Research Fellowship to MIC (NE/S014314/1). The EPSRC Centre for Doctoral Training in Aerosol Science (EP/S023593/1) provided studentship funding for J.W.K.

Publisher Copyright:
© 2022 American Chemical Society. All rights reserved.


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