Broadband Tunable Electron Paramagnetic Resonance Spectroscopy of Dilute Metal Complexes

Analysis
of the electron paramagnetic resonance (EPR) of transition ion complexes
requires data taken at different microwave frequencies because the
spin Hamiltonian contains operators linear in the frequency as well
as operators independent of the frequency. In practice, data collection
is hampered by the fact that conventional EPR spectrometers have always
been designed to operate at a single frequency. Here, a broadband
instrument is described and tested that operates from 0.5 to 12 GHz
and whose sensitivity approaches that of single-frequency spectrometers.
Multifrequency EPR from triclinic substitutional (0.5%) Cu­(II) in
ZnSO4 is globally analyzed to illustrate a novel approach
to reliable determination of the molecular electronic structure of
transition ion complexes from field-frequency 2D data sets.