Superheterodyne detection using a crossed-loop resonator permits obser
vation of species with long electron-spin-relaxation times without pas
sage effects and permits observation of dispersion spectra with higher
signal-to-noise than absorption spectra. This was demonstrated with S
-band (2.9 GHz) absorption and dispersion spectra for the defect cente
rs in gamma-irradiated fused SiO2 and for the radicals in coal. (C) 19
96 Academic Press, Inc.