Zerohyphen;field electron magnetic resonance (EMR) spectra have been observed for several dilute paramagnetic systems. Among these are peroxylamine disulfonate ions in aqueous solutions, Cr3+in single crystals of MgO, free radicals in xhyphen;irradiated powders of malonic acid, potassium hydrogen malonate, dipotassium malonate, succinic acid, and glutaconic acid. Zerohyphen;field spectra were observed by means of a marginal oscillatormdash;detector similar to that of Benedek and Kushida. The zerohyphen;field splittings in the systems studied were due exclusively to the hyperfine couplings between electronic and nuclear spins. Results obtained were in good agreement with highhyphen;field EMR measurements on these systems. In several cases the hyperfine couplings were obtained with greater precision than at high field. In addition, the radicalmdash;OOCsngbnd;Cdot;Hsngbnd;COOmdash;was identified, for the first time, in irradiated dipotassium malonate by means of its zerohyphen;field spectrum. No zerohyphen;field lines could be detected in electronhyphen;irradiated polyethylene. Advantages and disadvantages of the zerohyphen;field technique are discussed.
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