Principles of Electron Spin Resonance

The electron has associated with it a magnetic moment so it may be treated as a tiny bar magnet with magnetic moment given by 

The constant of proportionality g equals 2.0023 for a free electron and is called the spectroscopic splitting factor, or just the g factor. It is equivalent to the Lande g factor of atomic spectroscopy. 

In quantum mechanical terms, the allowable electron spin states are quantized, and the component of the electron spin vector in any given direction can only take one set of discrete values which are +s or —s, 

An ESR spectrometer thus measures the energy required to reverse the spin of an electron in an external magnetic field. Experimentally, this is performed by placing the substance containing unpaired electrons in an absorption cell in the form of a resonance cavity. The sample is 

The intensity, or area beneath the ESR absorption curve, is proportional to the number of unpaired spins in the sample, but since it is 

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Atherton, N.M., Principles of Electron Spin Resonance, Ellis Horwood, Chichester, 1993. 

N. M. Atherton Principles of Electron Spin Resonance, Ellis Horwood/Prentice Hall, Hemel Hempstad, 1993. [185] M. C. R. Symons Application of ESR Spectroscopy to the Study of Solvation, Pure Appl. Chem. 49, 13 (1977). [186] (a) L. R. Dalton, A. Bain, and C. K. Westbrook Recent Advances in Electron Paramagnetic Resonance, Annu. Rev. Phys. Chem. 41, 389 (1990). (b) J. H. Freed New Techniques in ESR, Annu. Rev. Phys. Chem. 57, 655 (2000). [187] G. R. Luck-... 

Principles of Electron Spin Resonance, edited by N.M. Atherton (Ellis Horwood PTR Prentice Hall, New York, 1993). 

Understand the basic principles of electron spin resonance and the information that this technique provides about free radical structure... 

Atherton NM (1993) Principles of electron spin resonance. Ellis Horwood, New York... 

C. P. Poole, H. A. Farach, The Theory of Magnetic Resonance, John Wiley Sons, New York, 1972 N. M. Atherton, Principles of Electron Spin Resonance, E. Horwood and PTR Prentice Hall, 1993. 

It does not seem necessary or advisable to describe once again the basic principles of electron spin resonance, since there are now available a substantial number of reviews and books dealing with these matters. Introductory articles have been written by Carrington S and Atherton S and there exist several text books S " s which treat the subject on a more quantitative level. Electron spin resonance papers have been regularly reviewed in the Chemical Society of London s Annual Reports and these articles may be used as guides to the more significant aspects of current developments in the field. Three features of an electron spin resonance spectrum are of interest the hyperfine splitting constants of any nuclei with non-zero spin in the molecule, the g-factor of the radical, and the widths of the various lines in the spectrum. 

Carrington A. The principles of electron-spin resonance. Endeavour 1962 21 51-57... 

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