Electron Paramagnetic Resonance Spectroscopy of Inorganic Materials

What is it about?

Electron Magnetic Resonance (EMR) is a group of closely related spectroscopic techniques including, apart from the most common CW-EPR (Continuous Wave Electron Paramagnetic Resonance), HF-EPR (high-field EPR), ENDOR (Electron Nuclear Double Resonance), ESRI (Electron Spin Resonance Imaging), and a number of Fourier Transform-based pulsed techniques (FT-EPR) such as ESEEM (Electron Spin Echo Envelope Modulation) or HYSCORE (Hyperfine Sublevel Correlation Spectroscopy). By probing stationary field dependent Zeeman splitting, H0(B), field independent interactions (fine, hyperfine and quadrupole couplings), H0, and time-dependent magnetic interactions, H(t), all together conventionally expressed in terms of the spin Hamiltonian H = H0(B) + H0 + H0(t), EPR provide an in-depth insight into the formation, local structure, dynamics, and reactivity of paramagnetic materials. The chemical information deduced from EPR may vary from simple confirmation of the presence of a given paramagnet to a more detailed description of its energy levels, ground state wave function (singly-occupied molecular orbital SOMO), spin density distribution at the paramagnetic centre and on the neighbouring atoms as well. First applications of EPR in the field of materials chemistry and related fields have been reported at the beginning of the 1960’s. Since then review articles have periodically appeared in the literature, whereas current literature surveys can be found in the RSC Specialist Periodical Reports - Electron Paramagnetic Resonance, which regularly include chapters dedicated to characterization of materials. With the advent of modern techniques such as FT-EPR and HF-EPR, when combined with computer simulation of the spectra, EPR has evolved into highly sophisticated and powerful research tool for exploring the materials with unpaired electrons.

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