Project Overview

Characterization of Reactive Transients in Heterogeneous Atmospheric Photochemistry

Faculty Sponsor

Ephraim Woods (




We developed a new experimental technique for understanding how sunlight can drive chemical reactions in atmospheric aerosol particles.The technique is called Time-resolved Photoelectric Activity of Aerosol, or TPEAA, and it is designed to detect the presence of very reactive and short-lived species created by sunlight. In the experiment, one laser pulse plays the role of sunlight and creates the short-lived species, then another laser pulse ejects electrons from the aerosol particle, a process called photoelectric charging. Because the electrons are most easily removed from the reactive species, the amount photoelectric charging is correlated to the amount of that species. We can then “watch” these transient molecules decay away by seeing the charging signal decrease as we change the time between the laser that creates them and the one that detects them. The continuing work on this project will investigate reactions that initate the formation of secondary organic aerosol and reactions involving the hydrated electron.

In a separate project, we will investigate the interaction of ozone with models of marine aerosol particles. The reaction of ozone with iodide in aqueous aerosol particles provides a sink for atmospheric ozone and creates halogenated neutral species in marine aerosol particles. Our experiment uses the photoelectric charging of aerosol particles to monitor the reaction of ozone with iodide near the surface of aqueous aerosol particles. Because iodide is a strong photoemitter under the conditions of our experiment, we can use the photoelectric activity as a proxy for the interfacial concentration of aqueous iodide.

Student Qualifications

The students should have some college-level chemistry background and should intend to major in chemistry, biochemistry, or a related field.

Number of Student Researchers

2 students

Project Length

8 or 9 weeks

Applications open on 01/03/2022 and close on 02/04/2022

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If you have questions, please contact Karyn Belanger (