Electron-Zeeman Resolved Electron Paramagnetic Resonance Spectroscopy

Abstract

Abstract Electron-Zeeman (EZ) resolved electron paramagnetic resonance (EPR) spectroscopy is introduced. In this two-dimensional pulse EPR technique a sinusoidal external field Δ B 0 ( t ) of variable amplitude is applied during the pulse sequence, resulting in a field-swept EPR spectrum that is spread into a second dimension, representing the g values of the paramagnetic species. The method can be used to improve the resolution of polycrystalline and single-crystal EPR spectra. For polycrystalline systems, simplified EPR spectra are obtained for fixed g values. For axial symmetry, these spectra allow direct access to coupling constants, also at orientations that differ from the principal axes orientations. Furthermore, overlapping resonances can be disentangled, extra-absorption peaks identified and unresolved hyperfine splittings observed. The sum projection onto the g -value axis corresponds in a g -value spectrum, which is free of hyperfine interactions. A detailed theoretical description of the EZ-EPR experiment is given. Several model calculations for systems with different symmetry of the magnetic interaction tensors are presented, and the versatility of EZ-EPR is demonstrated for different paramagnetic systems with g anisotropy.