A Novel Approach to Separating EPR Lines Arising from Species with Different Transition Moments

In pulsed EPR, spectral contributions from several species in one sample can be separated based on different EPR transition probabilities. This is usually done by monitoring the Rabi nutations in a 2D experiment. By using long pulses, the FID and echo shapes of species with different transition probabilities differ significantly, including temporal shifts of the observed echo signals in a two-pulse ESE experiment. These shifts can be used to disentangle spectral components in a 1D field-swept ESE experiment by choosing an appropriate detection time. This approach is demonstrated by experiments on a sample containing Mn²⁺ and Cr³⁺ centers as well as on an exchange-coupled Mn(III)/Mn(IV) system with Mn²⁺ contaminations.