Recombination of Atomic Oxygen on Surfaces

Catalytic surface recombination of atomic oxygen is studied in a flow system by paramagnetic resonance absorption and a comparison is made with platinum wire detectors for the same conditions of flow. Recombination of oxygen atoms on a fuzed quartz surface is found to follow first‐order kinetics with a surface recombination efficiency of 4.0×10^—5 per collision. Recombination on platinum wire detectors held at 200° and at 850°C is also found to be first order in oxygen atoms with surface recombination efficiencies of (0.01±0.002) and (0.1±0.02) per collision, respectively. Efficiencies for platinum are determined from the surface recombination heating and the strength of the oxygen‐atom magnetic resonance. The atom‐decay rate down the flow tube is found to be first order in oxygen atom with a dependence on the total pressure that suggests the homogeneous formation and subsequent reaction of ozone. The observed rates are consistent with the following scheme: $$\begin{array}{cc}\mathrm{O}+\mathrm{O}·\mathrm{S}\to {\displaystyle {lim}_{k_1}}{\mathrm{O}}_2\mathrm{+S}& \mathrm{(S=}\mathrm{surface}\mathrm{).}\\ \mathrm{O}+{\mathrm{O}}_2\mathrm{+M\to }{\displaystyle {lim}_{k_2}}{\mathrm{O}}_3\mathrm{+M}& \mathrm{(M=}\mathrm{third\; body}\mathrm{).}\\ \mathrm{O}+{\mathrm{O}}_3\to {\displaystyle {lim}_{k_3}}\text{2\hspace{0.17em}}{\mathrm{O}}_2.& \end{array}$$ The three‐body rate constant k₂ is found to have a value of 2.5×10¹⁴ cc² mole^—2 sec^—1.