School of Chemistry

Paul Seakins

Professor of Reaction Kinetics
Research section: Physical Chemistry

Contact details

Keywords

Reaction kinetics
Mechanisms of reactions
Atmospheric chemistry
Field studies

Research interests

Laboratory Studies of Elementary Reactions
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. Equally important is a quantitative knowledge of the branching fractions of multichannel reactions. Determination of these quantities is a stimulating challenge, revealing insights into reaction mechanisms as has been discussed in a recent review (Ref. 1). Much of the work is performed collaboratively with Profs Pilling and Heard and where possible the experimental measurements are supported by theoretical calculations (for example, see our special issue of Physical Chemistry, Chemical Physics (Ref. 2)).

HIRAC – A Highly Instrumented Reactor for Atmospheric Chemistry
Atmospheric 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 and deploy a range of state-of-the-art instrumentation to monitor stable species. Uniquely for such chambers, we are able to control both the temperature and pressure of the system and to deploy a laser based technique to measure the in situ concentrations of the radicals OH and HO2. The recent award of a grant from NERC will allow us to construct a cavity ring down (CRD) apparatus for measuring NO3 radicals. In the future CRD will be applied to the measurement of atmospherically important but challenging species such as glyoxal. The chamber will provide useful information to develop the Leeds Master Chemical Mechanism, a comprehensive chemical model of the Earth’s lower atmosphere. Full details of the chamber and initial results can be found in Reference 3.

Mobile Measurements of NOx and O3
Both local and national governments use air quality models to assess pollution at local (NO2) and regional (O3) spatial scales. One of the major aims of our work is to provide data to validate such models. High quality instrumentation mounted in fixed sites provides no spatial information but diffusion tubes, the preferred method for obtaining spatially resolved data, provide poor temporal resolution. Our approach has been to mount high temporal resolution NOx (NO2 and NO), CO, SO2 and O3 monitors in a mobile laboratory. We can either take data at fixed points or on the move (Ref. 4). Recently projects have included looking at NO to NO2 inter conversion in the urban environment and O3 concentrations as a function of distance from the coast and we are currently setting up a measurement programme in one of the tunnels on the Leeds Inner Ring Road.

Useful links

Details of research projects   
HIRAC group   
   

Selected publications

1. Product Branching Ratios from Simple Gas Phase Reactions’ Paul W. Seakins, Annu. Rep. Prog. Chem., Sect. C: Phys. Chem., 2007, 103, 173-222, DOI: 10.1039/b605650b

2. Synergies between Experimental and Theoretical Studies of Gas Phase Reactions – Editorial S.H. Robertson and P.W. Seakins, Physical Chemistry, Chemical Physics (or PCCP), 2007, 9, 4053-4054

3. Design of and initial results from a Highly Instrumented Reactor for Atmospheric Chemistry D.R. Glowacki, A. Goddard, K. Hemavibool, T.L. Malkin, R. Commane, F. Anderson, W.J. Bloss, D.E. Heard, T. Ingham, M.J. Pilling and P.W. Seakins*. Atmospheric Chemistry and Physics 2007, 7, 5371-5390

4. Measurement and modelling of air pollution and atmospheric chemistry in the U.K. West Midlands conurbation: Overview of the PUMA consortium project. R.M. Harrison, J. Yin, R.M. Tilling, X. Cai, P.W. Seakins, J.R. Hopkins, D.L. Lansley, A.C. Lewis, M.C. Hunter, D.E. Heard, L. J. Carpenter, D.J. Creasey, J.D. Lee, M.J. Pilling, N. Carslaw, K.M. Emmerson, A. Redington, R.G. Derwent, D. Ryall, G. Mills and S.A. Penkett. Science of the Total Environment 2006, 360, 5-25 doi 10.1016