Exchange Reaction of 18O Atoms with CO2 and with SO2 in Shock Waves

A shock tube coupled to a time‐of‐flight mass spectrometer has been used to study the reactions $$18\mathrm{O}+\mathrm{S}16\mathrm{O}\text{2→}\mathrm{S}16\mathrm{O}18\mathrm{O}\text{+16}\mathrm{O}\text{(1600°K\hspace{0.17em}<\hspace{0.17em}T\hspace{0.17em}<\hspace{0.17em}2100°K)}$$ and $$18\mathrm{O}+\mathrm{C}16\mathrm{O}\text{2→}\mathrm{C}16\mathrm{O}18\mathrm{O}\text{+16}\mathrm{O}\text{(2900°K\hspace{0.17em}<\hspace{0.17em}T\hspace{0.17em}<\hspace{0.17em}3425°K)}$$ in reflected shocks of mixtures of ¹⁸O₂, N₂O, SO₂, and of ¹⁸O₂ and CO₂, highly diluted with neon. The best values of the rate coefficients were $k_1{\text{\hspace{0.17em}=\hspace{0.17em}3.1\hspace{0.17em}±\hspace{0.17em}2.1\hspace{0.17em}×\hspace{0.17em}10}}^{\text{−12}}{\mathrm{cm}}^3/\mathrm{particle}·\sec$ at 2000°K, and $k_2{\text{\hspace{0.17em}=\hspace{0.17em}2.3\hspace{0.17em}±\hspace{0.17em}1.2\hspace{0.17em}×\hspace{0.17em}10}}^{\text{−12}}{\mathrm{cm}}^3/\mathrm{particle}·\sec$ at 3000°K. These rate coefficients, and also those deduced in an earlier study in this laboratory for the reactions ¹⁸O+C¹⁶O→C¹⁸O+¹⁶O and ¹⁸O+¹⁶O₂→¹⁶O¹⁸O+¹⁶O, are combined with the corresponding low‐temperature data of other workers to yield rate parameters which describe each reaction over a wide temperature range.