Investigation of OH reaction products. Excimer laser photolysis/slab laser fluorescence under tropospheric conditions

Absolute rate constants of OH reactions were measured up to total pressures of 1 bar and in the presence of strongly quenching gases. In the presence of O2, the effective disappearance rate of OH is diminished at all total pressures by a factor of 4 due to reproduction of OH by fast secondary processes. This can be described quantitatively by a reaction model, which includes a fast reaction of the OH+C2H2-adduct with O2, producing OH with a yield of 89 percent. Besides the decay of OH the formation and decay of vinoxy radicals as a minor intermediate product and the formation of glyoxal as a major product of the reaction in the presence of O2 could be followed with the LIF technique. Similar secondary reactions in the presence of O2 leading to reproduction of OH are found for the reactions of OH with propine and ethylenoxide.