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Electron Paramagnetic Resonance (EPR) Spectroscopy

  1. Brian J. Hales

Published Online: 15 MAR 2008

DOI: 10.1002/0470862106.ia336

Encyclopedia of Inorganic Chemistry

Encyclopedia of Inorganic Chemistry

How to Cite

Hales, B. J. 2008. Electron Paramagnetic Resonance (EPR) Spectroscopy. Encyclopedia of Inorganic Chemistry. .

Author Information

  1. Louisiana State University, Baton Rouge, LA, USA

Publication History

  1. Published Online: 15 MAR 2008


Electron-Paramagnetic Resonance (EPR) spectroscopy, also know as Electron-Spin Resonance (ESR) spectroscopy, monitors the energy levels of paramagnetic molecules. The major energy interaction (Zeeman Interaction) is between the magnetic moment of the electron and the field of a large uniform magnet. This interaction splits the normally degenerate spin levels of the electron and the electron-paramagnetic resonance (EPR) spectrometer measures the energy of this interaction. The EPR spectrometer is described along with a discussion of spectral optimization techniques. Additionally, energy interaction terms are described and include hyperfine coupling (the interaction of the magnetic moments of the unpaired electron and magnetic nuclei) and spin-orbit coupling, which influences the magnitude of the spectroscopic g-factor and the energy levels of S > 1/2 systems. The general features of half-integer and integer high-spin systems are further described, including examples.


  • bioorganometallic chemistry;
  • electron paramagnetic-resonance spectroscopy (EPR);
  • electron-spin resonance spectroscopy (ESR);
  • hyperfine interaction;
  • Zeeman interaction