Rate coefficients for the reaction of C2H with O2 at 90 K and 120 K using a pulsed Laval nozzle apparatus

Absolute rate coefficients for the reaction of C2H with O2 are measured at 90 K and 120 K by using a pulsed Laval nozzle apparatus with laser ionization, time-of-flight mass spectrometry (TOF-MS). The C2H radicals are generated by laser photolysis of C2H2 at 193 nm, and the products of the reaction with O2 and C2H2, HCCO and C4H2, respectively, are directly detected by laser ionization at 118 nm. Rate coefficients of (9.0±2.0)×10−11 and (5.0±1.5)×10−11 cm3 molecule−1 s−1 are obtained at 90 K and 120 K for the C2H+O2 reaction, respectively, by detecting the rise of the product HCCO.