The Donahue Group: Experimental Methods

Background

In all of our work, our approach is defined by the question, not the method. However, typically draw from a quiver of methods to answer experimental questions. These include specific analytical techniques and experimental systems. Systems include High Pressure Flow discharge flow kinetics, Environmental (Smog) Chambers, and Surface Reaction Instruments. The High Pressure Flow System (HPFS) was designed to function under a wide range of temperatures and pressures under truly wall-less conditions. We can carry out discharge flow experiments under the full range of pressures and temperatures encountered in the atmosphere (180K - 400K, 2 torr - 700 torr). This wide dynamic range in temperatures and pressures also allows us to expose subtelties of the potential energy surface for the chemical systems we investigate; stable intermediates and multiple transition states frequenly cause unusual behavior at low temperatures and high pressures.

Major Scientific Questions

• What governs the HOx-NOx partitioning of the upper troposphere and lower stratosphere?
• What controls ozone production efficiency in the urban atmosphere?
• What governs barrier heights in radical-molecule reactions?
• Why are some reactions direct and some indirect?

Recent Accomplishments and Current Work

• Understanding the fluid dymanics of the HPFS
• Measuring hydrocarbon-OH rate constants
• Elucidating reaction mechanisms
• Constraining HOx-NOx partitioning
• Exploring radical production in ozone-olefin reactions

Experimental Methods

• High Pressure Discharge Flow
• Reaction Modulation Spectroscopy

Measurement Techniques

• Laser Induced Flourescence
• Resonance Fluorescence
• UV absorption Spectroscopy
• FTIR absorption Spectroscopy
• FTUV absorption Spectroscopy
• Mass Spectrometry
• IR Cavity Ringdown Spectroscopy