Introduction to EPR

Electron Paramagnetic Resonance (EPR) – also known as Electron Spin Resonance (ESR) and, less commonly, Electron Magnetic Resonance (EMR) – is a powerful spectroscopic method for studying paramagnetic materials, i.e. those that contain (or can be induced to contain) unpaired electrons. Crudely, it can be considered as the electron spin equivalent of NMR spectroscopy. Like NMR, “EPR” covers a wide range of techniques including continuous wave, pulsed, double resonance and multi-dimensional methods.

Because the technique is sensitive and selective for the electron spin and its environment, EPR can be used to probe, for example:

  • Open-shell transition metal ions
  • free radicals (intrinsic, induced or labelled)
  • defects in materials
  • radical identity
  • spin-labelled materials
  • optically excited triplets
  • transient radicals (e.g. by spin trapping)
  • geometric and electronic structure
  • radical environment/surroundings
  • reaction mechanisms/kinetics
  • radical quantitation
  • electron transfer kinetics
  • electron spin dynamics
Textbooks on EPR vary widely in scope and complexity. Some of the standard texts are listed here:
  1. Electron Paramagnetic Resonance: A Practitioners Toolkit, M Brustolon, E Giamello (Eds) Wiley, Hoboken NJ, 2009.
  2. Biomolecular EPR Spectroscopy, W R Hagen, CRC Press, Boca Raton, 2008
  3. Nitroxides: Applications in Chemistry, Biomedicine, and Materials Science, G Likhtenshtein, J Yamauchi, S Nakatsuji, A I. Smirnov, R Tamura, Wiley-VCH, Weinheim, 2008.
  4. Electron Spin Resonance: Analysis and Interpretation, P.H. Rieger, Royal Society of Chemistry, Cambridge, 2007.
  5. Electron Paramagnetic Resonance: Elementary Theory and Practical Applications, J A. Weil, J R. Bolton, John Wiley & Sons Inc, New York, 2007
  6. Electron Spin Resonance Spectroscopy for Organic Chemists, F. Gerson, W. Huber, Wiley-VCH, Weinheim, 2003.
  7. Principles of Electron Spin Resonance (Ellis Horwood Series in Physical Chemistry), N.M. Atherton, Ellis Horwood, London, 1993.
  8. Electron Paramagnetic Resonance of d Transition Metal Compounds (Studies in Inorganic Chemistry), F.E. Mabbs, D. Collison, Elsevier, Amsterdam, 1992.
  9. Transition Ion Electron Paramagnetic Resonance J.R. Pilbrow, Clarendon Press, Oxford, 1991.
  10. Magnetic Atoms and Molecules, W. Weltner, Dover Publications Inc, Mineola NY, 1990
  11. Chemical and Biochemical Aspects of Electron Spin Resonance, M.C.R. Symons, Wiley, London, 1978.
  12. High-Field EPR Spectroscopy on Proteins and their Model Systems, K. Mobius and A. Savitsky, RSC Publishing, 2009.
  13. Principles of pulse electron paramagnetic resonance, A. Schweiger and G. Jeschke, OUP, 2001.
  14. Multifrequency Electron Paramagnetic Resonance: Theory and Applications, Sushil K. Misra, Wiley-VCH, 2011, ISBN-13: 978-3-527-40779-8
  15. Stable Radicals: Fundamentals and Applied Aspects of Odd-Electron Compounds, Robin Hicks (Editor), Wiley-VCH, 2010, ISBN-13: 978-0-470-77083-2
  16. Carbon-Centered Free Radicals and Radical Cations: Structure, Reactivity, and Dynamics (Wiley Series of Reactive Intermediates in Chemistry and Biology), Malcolm D. Forbes (Editor), Wiley-Blackwell, 2010, ISBN-13: 978-0470390092
  17. Electron Paramagnetic Resonance of Transition Ions (Oxford Classic Texts in the Physical Sciences), A. Abragam and B. Bleaney, OUP, April, ISBN-13: 978-0199651528
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