Contributions of Intersystem Crossing and Reaction in the Removal of CH2(A1A1) by Hydrocarbons Studied with Laser Magnetic Resonance (LMR)

摘要

The formation of ground state CH2 (X 3B1)-radicals in the collisional removal of CH2 (A1A1) by selected hydrocarbons was studied in the gas phase at room temperature using Laser Magnetic Resonance (LMR). The radicals were generated by excimer laser photolysis of CH2CO at 308 nm in the presence of varying concentrations of RH. The yields of CH2 (X3B1) produced by intersystem crossing were measured with the LMR. Presuming the primary quantum yield for CH2 (X3B1) formation in the CH2CO photodissociation to be 0, the branching ratios for intersystem crossing were found. For values 0 the results have to be regarded as upper limits. Hence, for all hydrocarbons studied, reactive quenching is the dominating CH2 (a1A1) removal pathway.