Dr Stephen Ball

Dr Stephen Ball

Senior Lecturer in Atmospheric Chemistry

Tel: +44 (0)116 252 2139

Email: Withheld

Research Group: Atmospheric Chemistry

Personal Details

  • Fellow of the Higher Education Academy

Publications

  1. “Modelling molecular iodine emissions in the coastal marine environment: the link to new particle formation”, A. Saiz-Lopez, J.M.C. Plane, G. McFiggans, S.M. Ball, M. Bitter, R.L. Jones, C. Hongwei and T. Hoffman, Atmos. Chem. PhysDiscuss., 5, 5405-5439, 2005.
  2. “Small scale structure in the atmosphere: implications for chemical structure and observational methods”, R.L. Jones, S.M. Ball and D.E. Shallcross, Faraday Discussions 130, DOI: 10.1039/b502633b, 2005
  3. “A broadband cavity ringdown spectrometer for in-situ measurements of atmospheric trace gases”, M. Bitter, S.M. Ball, I.M. Povey and R.L. Jones, Atmos. Chem. Phys. Discuss., 5, 3491-3532, 2005.
  4. Broadband cavity enhanced absorption spectroscopy using light emitting diodes, S.M. Ball, J.M. Langridge and R.L. Jones, Chemical Physics Letters398, p68, 2004
  5. Broadband cavity ringdown spectroscopy, S.M. Ball and R.L. Jones, Chemical Reviews 103, p5239, 2003
  6. Broadband cavity ringdown spectroscopy of the NO 3 radical, S.M. Ball, I.M. Povey, E.G. Norton and R.L. Jones, Chemical Physics Letters342, p113, 2001.

Research

Optical absorption spectroscopy is widely applied in the atmospheric sciences to measure trace gases. The results of such measurements are used in environmental monitoring and for validation of results from computer models of the atmosphere. Optical methods have the distinct advantages that the target species is identified unambiguously and its concentration is obtained directly. But many of the most interesting species - the radicals that drive chemical reactions in the atmosphere - are typically present in such small concentrations that it is necessary to perform absorption measurements over very long optical paths. Unfortunately, the use of extended optical paths necessarily introduces the issue of spatial averaging, which can mask important local variations in the chemistry of short-lived species. Another method is required.

Our work incorporates the recently developed technique of cavity ringdown spectroscopy (CRDS) into instruments for atmospheric field measurements. In CRDS, direct measurements of an absorber's concentration are provided by monitoring the temporal decay of laser light trapped inside a cavity composed of two or more highly reflective mirrors. With the very high quality of optics now available, optical paths of many kilometres are accessible in a compact instrument. Consequently, CRDS instruments are portable and can be deployed in a variety of applications to explore the local atmospheric sources, sinks and variability of short-lived reactive trace species.

One of the species we have chosen to study is the nitrate radical (NO3). This species dominates the oxidation of a range of natural and anthropogenic source gases in the night-time troposphere. The figure shows the absorption spectrum of a laboratory sample of NO3 recorded by our CRDS instrument, with spectra of other important trace gases below. Our instruments are deployed to measure ambient levels of NO3 radicals, iodine compounds and other short-live gases during field experiments, for example, during the North Atlantic Marine Boundary Layer Experiment (Mace Head, Ireland).

Dr Ball-Absorption Spectrum

"I welcome scientific enquiries from colleagues and students about any aspect of my research. I prefer not to receive commercial or advertising material. Therefore data acquired from my webpage(s) must not be processed for marketing purposes."

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Contact Details

Department of Chemistry

University of Leicester

University Road

Leicester

LE1 7RH

UK

 

email: chemistry@le.ac.uk

Tel: 0116 252 2100

Fax: 0116 252 3789