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 $\text{g‖\hspace{0.17em}=\hspace{0.17em}2.0035\hspace{0.17em}±\hspace{0.17em}0.0001}$ and $\text{g⊥\hspace{0.17em}=\hspace{0.17em}2.0220\hspace{0.17em}±\hspace{0.17em}0.0001}$ , whereas at 77°K, $\text{g‖\hspace{0.17em}=\hspace{0.17em}2.0028\hspace{0.17em}±\hspace{0.17em}0.0001}$ and $\text{g⊥\hspace{0.17em}=\hspace{0.17em}2.0242\hspace{0.17em}±\hspace{0.17em}0.0001}$ . 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.