Time resolved detection of OH by long path absorption using a cw-laser - kinetics of reactions of OH in air at one atmosphere

A laser detection method for OH in the uv at 308 nm has been developed for the study of the kinetics of OH under environmental conditions (air at atmospheric pressure and variable humidity). The experimental setup consists of a long path absorption cell, a uv cw laser as analytical light source, a differential photodiode detection system an excimer laser for the pulsed production of OH radicals. A detection limit for OH of 10 E7 cm E-3 is obtained at 40 mys rise time. First results on rate constant measurements for the reaction of OH with C2H2 and of OH with CO at 1 atm are presented, where interfering consecutive radical reactions have definitely been excluded. (ITA)