ESR Study of the Ozonide Ion in γ-Irradiated Sodium Bromate

The identification of a paramagnetic center in γ-irradiated sodium bromate crystals as the ozonide ion, O3−, is confirmed. At ambient temperatures the principal values of the axially symmetric g tensor are found to be g‖ = 2.0035 ± 0.0001 and g⊥ = 2.0220 ± 0.0001, whereas at 77°K, g‖ = 2.0028 ± 0.0001 and g⊥ = 2.0242 ± 0.0001. If the O3− ion is a bent molecule of bond angle 110 ± 5° the electron spin resonance data suggests that the O3− ion is undergoing rapid motion at ambient temperatures and that the rate of motion is reduced at 77°K. Because no bromine-containing radical is characterized after the ambient temperature irradiation of sodium bromate, the electron spin resonance results suggest a radiolytic decomposition differing from that of the alkaline-earth bromates, in which the paramagnetic species BrO2 is postulated.