Ion—Molecule Reactions in an O2+–H2O System

Abstract

A sequence of reactions which occur in ionized O₂–H₂O mixtures has been studied with the following results: $${\mathrm{O}}_2^{+}+{\mathrm{H}}_2\mathrm{O}+\mathrm{M}\to {\mathrm{O}}_2^{+}·{\mathrm{H}}_2\mathrm{O}+\mathrm{M}\text{,\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}k=0.9,\hspace{0.17em}2.8,\hspace{0.17em}}\mathrm{and}{\text{\hspace{0.17em}2.0×10}}^{\text{−28}}\hspace{0.17em}{\mathrm{cm}}^6\hspace{0.17em}{\sec }^{\text{−1}}\hspace{0.17em}\mathrm{for}\hspace{0.17em}\mathrm{M}=\mathrm{He}\mathrm{,\hspace{0.17em}}{\mathrm{N}}_2\mathrm{,\hspace{0.17em}}\mathrm{and\; Ar},$$ $${\mathrm{O}}_4^{+}+{\mathrm{H}}_2\mathrm{O}\to {\mathrm{O}}_2^{+}·{\mathrm{H}}_2\mathrm{O}+{\mathrm{O}}_2{\text{,\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}k=2.2×10}}^{\text{−9}}\hspace{0.17em}{\mathrm{cm}}^3\hspace{0.17em}{\sec }^{\text{−1}},$$ $${\mathrm{O}}_2^{+}·{\mathrm{H}}_2\mathrm{O}+{\mathrm{H}}_2\mathrm{O}\to {\mathrm{H}}_3{\mathrm{O}}^{+}·\mathrm{OH}+{\mathrm{O}}_2{\text{,\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}k=1.9×10}}^{\text{−9}}\hspace{0.17em}{\mathrm{cm}}^3\hspace{0.17em}{\sec }^{\text{−1}},$$ $$\to {\mathrm{H}}_3{\mathrm{O}}^{+}+\mathrm{OH}+{\mathrm{O}}_2{\text{,\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}k≤ 3× 10}}^{\text{−10}}\hspace{0.17em}{\mathrm{cm}}^3\hspace{0.17em}{\sec }^{\text{−1}},$$ $${\mathrm{H}}_3{\mathrm{O}}^{+}·\mathrm{OH}+{\mathrm{H}}_2\mathrm{O}\to {\mathrm{H}}_3{\mathrm{O}}^{+}·{\mathrm{H}}_2\mathrm{O}+\mathrm{OH}{\text{,\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}k=3×10}}^{\text{−9}}\hspace{0.17em}{\mathrm{cm}}^3\hspace{0.17em}{\sec }^{\text{−1}}.$$ The measurements were made at 295°K in a flowing afterglow system, operated in both fixed and variable reaction length modes. The results indicate that $\mathrm{D(}{\mathrm{O}}_2^{+}·{\mathrm{H}}_2\mathrm{O}\mathrm{)〉D(}{\mathrm{O}}_2^{+}·{\mathrm{O}}_2\mathrm{),\hspace{0.17em}D(}{\mathrm{H}}_3{\mathrm{O}}^{+}·{\mathrm{H}}_2\mathrm{O}\mathrm{)\gtrsim D(}{\mathrm{H}}_3{\mathrm{O}}^{+}·\mathrm{OH})$ .