CH3 state distributions form the reactions of O(1D) with saturated and chlorinated hydrocarbons

Abstract

CH3 product state distributions arising from the reaction of O(1D) with CH4, C2H6, C3H8, and i-C4H10 were characterized using resonantly enhanced multiphoton ionization (REMPI). The vibrational distributions in the ν1 symmetric stretch and in the ν2 ‘‘umbrella’’ mode are noninverted in all cases. The results are compared to statistical adiabatic channel-phase space theory (SACM-PST) calculations. The ν2 excitation is much less excited than statistically expected for the reactions with CH4 and C2H6 but nearly statistical in the case of the heavier hydrocarbons. For all reactions but the one with C2H6, the ν1 excitation is similar to the distribution statistically expected. The CH3 rotational distribution from the reaction of O(1D) with CH4 is much hotter than room temperature as comparison with simulated rotational band contours showed. From the integrated CH3 band intensities, we obtained approximate reaction cross sections for the CH3 channel with a decrease in the order CH3≳C2H6≳C3H8≳i-C4H10. In the reactions of O(1D) with CH3Cl, CH3CH2Cl, and CH3CH2CH2Cl, we observed CH3 as a primary product. CH3–ν1 excitation is small in all cases but ν2 excitation is considerable with even an inverted v=1/v=0 distribution in the case of the reaction with C2H5Cl. The relative reaction cross sections for the CH3 channel decrease in the order CH4≫CH3Cl≳CH3CH2Cl≳CH3CH2CH2Cl.