A NOVEL LASER-BASED TECHNIQUE FOR THE TIME-RESOLVED STUDY OF INTEGRATED HYDROCARBON OXIDATION MECHANISMS

An experimental method has been developed to study the formation of OH radicals and of NO2 in the integrated oxidation chain of hydrocarbons under NO(x)-rich tropospheric conditions. In this technique the oxidation of hydrocarbons is initiated by laser pulse photolysis of Cl2 and the temporal behaviour of OH and NO2 is monitored by direct time-resolved cw-laser absorption and LIF, respectively. Combined with computer modelling of the complete oxidation mechanisms the results allow the determination of (I) the extent of NO/NO2 conversion and hence the ozone formation potential of individual hydrocarbons and (II) the branching ratio of HO2 formation relative to other reaction channels of alkoxy radicals. First applications of this technique to the oxidation of C2H6 and C3H8 are presented.