MEASUREMENT OF OH AND HO2 RADICAL UPTAKE COEFFICIENTS ON WATER AND SULFURIC-ACID SURFACES

A wetted wall flow tube reactor was used to measure the uptake coefficients, gamma, of OH and HO2 on pure water at 275 K and 28% w/w sulfuric acid at 249 K. The uptake coefficients are lower limits to the mass accommodation coefficients, alpha, and they were determined to be 0.0035 for OH and >0.01 for HO2 on liquid water and >0.08 for OH and >0.05 for HO2 on the sulfuric acid solution. In addition, the binary diffusion coefficients for HO2 and OH in water vapor were estimated to be 79 +/- 8 and 116 +/- 20 Torr cm2 s-1, respectively, at 275 K. The determination of uptake coefficients using wetted wall flow tube reactors is described including the effect upon gamma of gas-phase diffusion, solvation, and reaction within the liquid.