General Magnetic Transition Dipole Moments for Electron Paramagnetic Resonance

TL;DR

This paper derives general formulas for magnetic transition rates in electron paramagnetic resonance experiments, applicable to various spin systems and excitation geometries, enhancing the understanding of EPR transition mechanisms.

Contribution

It introduces a comprehensive theoretical framework for magnetic transition dipole moments in EPR, applicable to anisotropic spin systems with diverse experimental configurations.

Findings

Determined parities of high-spin Fe(III) states using polarization-dependent EPR.

Provided general expressions for magnetic transition rates in anisotropic spin systems.

Applicable to various excitation geometries and polarization states.

Abstract

We present general expressions for the magnetic transition rates in beam Electron Paramagnetic Resonance (EPR) experiments of anisotropic spin systems in the solid state. The expressions apply to general spin centers and arbitrary excitation geometry (Voigt, Faraday, and intermediate). They work for linear and circular polarized as well as unpolarized excitation, and for crystals and powders. The expressions are based on the concept of the (complex) magnetic transition dipole moment vector. Using the new theory, we determine the parities of ground and excited spin states of high-spin (S = 5/2) Fe(III) in hemin from the polarization dependence of experimental ground state EPR line intensities.