Continuous-wave EPR at 275Â GHz: Application to high-spin Fe3+ systems

► 275 GHz continuous-wave EPR spectroscopy on high-spin Fe3+ systems using a specialized single-mode cavity. ► Sensitivity and signal stability are illustrated on dilute solutions of Fe(III)-EDTA and rubredoxin. ► Zero-field-splitting parameters and g-anisotropy were determined accurately by simulation of the spectra.