INVERSION-RECOVERY DETECTED EPR

Inversion-recovery detected EPR is introduced. This field-swept EPR method is based on a periodically repeated inversion recovery experiment, with detection of the first harmonic of the periodically oscillating transverse magnetization. With inversion-recovery detected EPR, pure absorption spectra are obtained with signal amplitudes depending on the repetition rate of the investing pi pulses and on the strength of the probe field. The technique is particularly well suited for the measurement of broad EPR lines and for separating overlapping spectra of paramagnetic species with different spin-lattice relaxation times T-1. The experiment is analyzed theoretically and some of the predicted features are experimentally verified. Inversion-recovery detected EPR spectra of a single crystal, a polycrystalline and a liquid solution sample are presented, and the separation of overlapping spectra is demonstrated.