EPR and ESR are two names of the same technique (EPR is preferred by the chemists and biologists while ESR is a favorite of physicists) which depends on detecting transitions between the magnetic field-split spin sublevels in systems with unpaired electrons, in particular, in paramagnets.
It has proven an indispensable tool in a large range of applications in physics, materials science, chemistry and biology, including studies of impurity states, molecular clusters, natural or induced radicals, optically excited paramagnetic states, electron spin-based quantum information devices, transition-metal based catalysts; and for structural and dynamical studies of metalloproteins, spin-labeled proteins and other complex bio-molecules and their synthetic models.
EPR/ESR when performed at high frequencies (hundreds of GHz rather than conventional 9 or 35 GHz) and high fields (up to 45 T instead of 0.3 – 1.2 T), correspondingly named HFEPR/HFESR, offers distinct advantages over traditional measurements. HFEPR/HFESR experiments can be crudely categorized as high resolution or broadband. In the former case, one concentrates on the g ~ 2 spectral region and studies it in great detail, often using pulsed techniques. This technique is appropriate mainly to radicals and defects. Broadband HFEPR/HFESR experiments cover a full frequency/field space and are particularly suitable to studying paramagnetic metal complexes and their clusters.
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Krzystek, J., et al, Multi-frequency, high-field EPR as a powerful tool to accurately determine zero-field splitting in high-spin transition metal coordination complexes, J. Coord. Chem. Rev., 250 (2006) Read online.
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Last modified on 22 August 2023