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.