Anisotropic proton hyperfine interaction in the electron spin resonance spectrum of the ethyl radical

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Abstract
The ESR spectrum of the ethyl radical isolated in an argon matrix at 4.2°K has been measured. The radical was produced by the photolysis of a mixture of C2H4 and HI with radiation from a high‐pressure mercury lamp. From a line‐shape analysis of the observed spectrum, the following anisotropic hyperfine interaction parameters for the α and β protons, and g values have been obtained: A ⊥ α =19.4± 0.5 G , A ∥ α =29.6± 0.5 G , A ⊥ β =25.9± 0.5 G , A ∥ β =28.7± 0.5 G , g av =2.0023± 0.0003 (Δ g= g ∥ − g ⊥ ≤ 0.0003) . These ESR parameters provide the first experimental assessment of currently available theoretical results on the proton hyperfine anisotropy in C2H5.