Current Research Topics and Tools

Heterogeneous Reactions

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We use a variety of flow reactors to measure heterogeneous reaction rates and mechanisms using vacuum ultraviolet photoionization mass spectrometry and aerosol X-ray photoelectron spectroscopy at the Advanced Light Source.

Trapping of Droplets

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We design and build quadrupole traps to electrodynamically levitate droplets arrays. These clouds of trapped droplets allow us to measure heterogeneous reactions over long timescales (days) that more closely approximate the atmosphere.

Droplet Collisions

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We use high speed collisions of micron-sized droplets to initiate a chemical reaction (such as the pH jump, which turns on a fluorescent dye as shown above). Droplet collisions enable fast mixing of reactants and allows us the possibility to observe transient intermediates produced in bimolecular condensed phase reactions.

Research Tools

We use a variety of commercial and home-built instrumentation to do our research

Vacuum Ultraviolet (VUV) Aerosol Mass Spectrometry

We use VUV aerosol mass spectrometry to measure the change in chemical composition of an aerosol undergoing a heterogeneous reaction. This allows us to measure reaction product distributions and heterogeneous kinetics, required for developing detailed reaction mechanisms.

Aerosol Photoemission

In collaboration with Drs. Oleg Kostko and Musa Ahmed, we use velocity map imaging X-ray photoelectron spectroscopy to measure the oxidation state and functional group distribution at aerosol surfaces undergoing heterogeneous reactions.

Atmospheric Pressure Mass Spectrometry

We have adapted a number of commercial ionization sources (DART and ESI) to measure real time nanoparticle and droplet chemistry. These ionization source are coupled to a Thermofisher Orbitrap and Velos Pro mass spectrometer for high resolution mass analysis.

Stochastic Reaction Diffusion Simulations

In collaboration with Dr. Frances Houle (LBNL) we use reaction diffusion simulations to model experimental heterogeneous kinetics, which affords deeper insight into molecular reaction mechanisms at droplet and aerosol interfaces. We use the open access software program, Kinetiscope, developed by William Hinsberg and Frances Houle.