THE REACTION OF OH WITH C2H2 AT ATMOSPHERIC CONDITIONS INVESTIGATED BY CW-UV-LASER-LONGPATH-ABSORPTION OF OH

A sensitive cw-UV laser absorption method at 308 nm has been used to investigate the pressure dependence of the kinetics of OH reactions with C//2H//2. OH radicals are generated by excimer laser photolysis of H//2O at 193 nm or of H//2O//2 at 248 nm. Using an absorption light path of 151 m and accumulating 50 decay curves, OH concentrations in the range from 10**1**0 down to 10**7 cm** minus **3 can be detected in the presence of N//2 at 10-1000 mbar. The experimental data on the pressure dependence of the rate constant for the reaction of OH with C//2H//2 in N//2 yield the limiting values.