STATE-SELECTIVE INVESTIGATION OF CHEMICAL-REACTIONS BY LASER FLUORESCENCE AND IONIZATION

CH3 product state distributions arising from the reaction of O(D-1) wi th CH4 and C2H6 were characterized using Resonant Multiphoton Ionizati on (REMPI). The vibrational distributions in the v(1) symmetric stretc h and in the v(2) ''umbrella'' mode are noninverted. The results are c ompared to Statistical Adiabatic Channel-Phase Space Theory (SACM-PST) calculations. The v(2)-excitation for both reactions is lower than st atistically expected. The v(1) mode for the O(D-1)/CH4 reaction is les s excited than the statistical estimate, while the v(1) distribution f rom the C2H6/O(D-1) reaction is hotter than the SACM-PST-distribution. As an example for state selective investigation of chemical reactions by Laser Induced Fluorescence (LIF), the reaction H + O-2 was studied using translationally excited H atoms from HI photolysis in the range 227-300 nm. An increase in the reaction probability with increasing c ollision energy up to 175 kJ/mol followed by a decrease at higher E wa s observed. Absolute reaction cross sections at different collision en ergies were measured with a calibration method using HNO3 photolysis a s a reference. The experimental values are compared with cross section s from trajectory calculations on ab initio H + O-2 potential surfaces .