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The electron spin resonance method was employed to study the nature, concentration and kinetics of the disappearance under varying conditions of radicals produced in polyethylene by fast electron irradiation at 77°K. The predominant radical species at 77°K is the alkyl radical —CH 2 —ĊH—CH 2 —. On being warmed to room temperature it disappears rapidly, revealing a more stable un­identified radical. The kinetics of the decay at room temperature of both radicals was observed. Their stabilities were found to vary in polyethylene samples of differing physical and chemical properties. G values for these radicals are given. Comparison was made with spectra obtained under similar conditions with two pure paraffins and a pure olefin to evaluate the effect of crystallinity branching, molecular weight and unsaturation. In the olefin there is evidence for a build-up of allyl radicals due to the encounter of an alkyl radical with main chain unsaturation. This supports the view that alkyl radicals are mobile, and cross-linking occurs when two such radicals meet.

Reflected-shock gas mixtures of C2ClF3, CF4, and C2F4 in excess argon were used to produce emission spectra of the C2(A 3Π—X 3Π) and CF(A 2Σ+—X 2Π) band systems. Absolute intensities of these electronic transitions were measured at several different wavelengths. Spectral data analyzed with equilibrium C2 and CF concentrations based on current JANAF heats of formation of the CF2 and CF radicals yielded for the Swan system the oscillator strength f(0, 0) in emission, 0.017±0.005 and for the CF system, 0.046±0.014. By reduction of the same data with recent shock-tube heats of formation, the oscillator strength f(0, 0) for the Swan system was 0.028±0.009 and that for the CF system, 0.0051±0.0015.