MULTIFREQUENCY ELECTRON-PARAMAGNETIC RESONANCE SPECTROSCOPY

Over the past decade, the advantages of performing electron paramagnetic resonance (EPR) experiments outside of the standard 9- to 35-GHz range have become increasingly exploited For example, low-frequency (<9 GHz) EPR experiments may lead to increased spectral resolution or enhance features due to ''forbidden'' transitions. High-frequency (>35 GHz) experiments also may result in enhanced resolution or allow for more accurate determinations of zero-field splittings in high-spin systems or details of motion not observable at lower frequencies. The selective review presented here emphasizes applications of low- and high-frequency EPR spectroscopy with special emphasis on multifrequency applications in coal research.