Electron paramagnetic resonance (EPR) or electron spin resonance (ESR) spectroscopy is a technique for studying materials with unpaired electrons. The basic concepts of EPR are analogous to those of nuclear magnetic resonance (NMR), but it is electron spins that are excited instead of the spins of atomic nuclei. Because most stable molecules have all their electrons paired, the EPR technique is less widely used than NMR. However, this limitation also means that EPR offers great specificity, since ordinary chemical solvents and matrices do not give rise to EPR spectra.
EPR was first observed in Kazan State University by Soviet physicist Yevgeny Zavoisky in 1944, and was developed independently at the same time by Brebis Bleaney at the University of Oxford.
Read more about Electron Paramagnetic Resonance: Spectral Parameters, Pulsed EPR, Applications, High-field High-frequency Measurements
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“It is closing time in the gardens of the West and from now on an artist will be judged only by the resonance of his solitude or the quality of his despair.”
—Cyril Connolly (1903–1974)