We present a direct kinetic study of the third-order recombination reaction K + 02 + Nz--*KO2 + N2 (k4) across the temperature range 680-1010K. K(42S~t2) was generated by pulsed irradiation and monitored by timeresolved atomic resonance absorption spectroscopy in the "single shot mode" in the presence of 02 and N2 using the Rydberg transition at ~ = 404 nm (K(52Pj) ~ K(42S~/2)). While the resulting data for k4 can be empirically expressed within this temperature range by the form k4(680-1010K) = (6.63 _+ 0.66 x 10-23)(T/K) -2"6±°'28 cm 6 molecule -2 s t, a full extrapolation based on the unimolecular rate theory of Tr6e was carried out in order to extend the data to flame temperatures (2000K), given the importance of potassium additives in flame inhibition. The full extrapolation across the range 200-2000K can be expressed to within 10% by ln(k,/cm 6 molecule-2 s-I) = _ 0.2558 [In( T/K)] 2 + 1.361 In(T/K) -66.14.
These results are compared with data derived from measurements on a fast flow reactor which show a much smaller temperature dependence and indicate an extrapolated value for ka at flame temperatures significantly higher than derived from the present investigations.