Professor Paul Seakins

Profile

HIRAC group

Research interests

Laboratory Studies of Reactions Relevant for Combustion, Atmospheric and Fundamental Chemistry
An understanding of the kinetics of elementary reactions involving small radical species is vital for developing chemical models of complex phenomena such as combustion or atmospheric chemistry. Many important reactions have multiple product channels and a focus of our work has been to quantify branching ratios between products as well as the overall rate coefficients.

A recent high light published in Science (Ref 1) has been in identifying the role of chemical activation in controlling the branching ratio of the atmospherically important OH + C2H2/O2 reaction to yield glyoxal or formic acid. This work exemplifies our approach; we look for reactions which are fundamentally interesting, but also of relevance. Other studies include the atmospheric oxidation of amines important in Carbon Capture and Storage (Ref 2), and studies of reactions involved in dimethyl ether (DME) combustion, relevant for the development of new generations of cleaner vehicle engines. Our work is supported by grants from NERC and EPSRC and we are particularly excited by a new application to apply our knowledge and techniques to reactions important for planetary atmospheres. Much of the work is performed collaboratively with Profs Heard, Plane and Pilling, and where possible, the experimental measurements are supported by theoretical calculations (e.g. Ref 1).

HIRAC: A Highly Instrumented Reactor for Atmospheric Chemistry
HIRAC is a 2200 litre atmospheric chamber equipped with state-of-the-art instruments that allow the detection of stable products (e.g. GC, FTIR), but uniquely for such a chamber also OH and HO2 radicals, key intermediates in atmospheric chemistry. Chambers such as HIRAC help to bridge the gap between laboratory measurements of individual elementary reactions (as mentioned above) and the complexity of the real atmosphere. In the chamber we can control the conditions (e.g. temperature, pressure, light intensity, composition) simplifying the chemistry.

A current area of interest is the chemistry in environments dominated by biogenic emissions (e.g. isoprene), but where anthropogenic pollutants such as NO are low. Field campaigns (including those by Prof Heard) have observed higher than expected OH levels and we need to understand these observations, as OH controls the methane lifetime in turn effecting global warming. We have studied the yield of OH and HO2 from the ozonolysis of isoprene (Ref 3) and are currently looking at OH yields from RO2 + HO2 reactions and have other projects on isoprene chemistry. HIRAC provides useful information to develop the Leeds Master Mechanism, a comprehensive model of the troposphere. The controlled conditions of HIRAC make it an excellent resource to evaluate and calibrate field instrumentation.

We are also interested in urban environments and a new PhD student is building on our field measurements of NOx emissions from a nearby tunnel (Ref 4) to look at ozone forming potentials and OH lifetimes of real exhaust emissions.

Research groups and institutes

• Atmospheric and Planetary Chemistry