Abstract: The relaxation-matrix theory of line width analysis in electron spin resonance spectra has been used to analyze the alternating line width effects arising from the motion of β protons of propagating radical, this motion was treated by using a Brow-nian motion model assuming a torsional oscillations about the C_α—C_β bond. The formula of line-width for β-protons obtained were applied to the analysis of the ESR spectra for styrene radicals in the whole process of bulk polymerization to explain the time dependence on polymerization. The results also support the assignment of the β protons hfs-constants.

Key words: Alternating broaden effect, ESR, Propagating radical, Styrene