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EPSRC National Service for Electron Paramagnetic Resonance Spectroscopy

Introduction to Electron Paramagnetic Resonance

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, ie. 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 (eg. by spin trapping)
  • geometric and electronic structure
  • radical environment/surroundings
  • reaction mechanisms/kinetics
  • radical quantitation
  • electron transfer kinetics
  • electron spin dynamics