Hyperfine Spectroscopy – ENDOR

2016 - Volume 5 eMagRes
Volume 5, Issue 4
Jeffrey R. Harmer

Jeffrey R. Harmer

Center for Advanced Imaging, University of Queensland, St Lucia, Queensland, Australia

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First published: 15 December 2016
Citations: 31

Abstract

Electron–nuclear double resonance (ENDOR) is a widely used technique to measure the nuclear frequencies of paramagnetic centers in solution, single crystals, and disordered systems such as powders and frozen solutions. This article starts with a theoretical overview of the energy levels and corresponding ENDOR spectra of low- and high-spin systems in the strong and weak coupling regimes. Advantages of high-field ENDOR are considered. The basis of CW ENDOR and triple CW ENDOR is then explained. The important concepts behind pulse ENDOR techniques are then introduced, starting with 1D Davies and 1D Mims ENDOR, triple, and followed by two-dimensional techniques that aim to increase the information content extractable from the data. Methods to determine the sign of the hyperfine coupling are described, as well as the advantages of stochastic RF excitation, nonlinear acquisition schemes, and echo train detection sequences that are designed to increase experiment stability and sensitivity.

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