Kinetic studies of aromatic radical reactions by cavity-ringdown spectroscopy

The cavity ringdown (CRD) technique has been applied to measure the absolute rate constants of C₆H₅ radical reactions relevant to incipient soot formation. The high sensitivity of the CRD technique allows us to determine reproducibly the absolute values of rate constants to as low as 10^-16-10^-15 cm³/molecule·s, which is as good as what can be achieved by the laser-induced fluorescence technique for fluorescing species. The absolute rate constants for reactions with NO, O₂, C₂H₂, C₂H₄, i-C₄H₁₀, (i-C₃H₇)₂, cycloalkanes (C₅H₁₀ - C₈H₁₆), CCl₄, HBr and DBr have been determined over the temperature range 297-523 K. The mechanisms involved in these reactions are discussed.