Measurement of absolute rate data for the reaction of atomic potassium, K(4²S½), with CH₃F, C₂H₅F, C₆H₅F, CH₃Br, C₂H₅Br, HCl and HBr by time‐resolved atomic resonance absorption spectroscopy at λ = 404 nm (K(5²PJ) ← K(4²S½))

We present a kinetic study of atomic potassium in its electronic ground state, K(4 2 S ½ ), generated in the “single‐shot mode” by pulsed irradiation at elevated temperatures and monitored by time‐resolved atomic resonance absorption spectroscopy using the Rydberg doublet at λ = 404 nm (K[5 2 P J ]←K[4 2 S ½ ]). Profiles for the decay of atomic potassium in the presence of various halogenated reactants were recorded at different temperatures, yielding the following Arrhenius parameters ( k R = A exp(− E / RT ), errors 1σ): R A /10 −10 cm 3 molecule −1 s −1 E / kJ mol −1 Temp. Range CH 3 F 1.93 +1.1 −0.7 59±3.3 822–922 K C 2 H 5 F 1.40 +2.5 −0.9 62±6.6 694–807 K C 6 H 5 F 2.0 +1.6 −0.9 41±3.9 705–812 K CH 3 Br 1.7 +0.3 −0.2 15.9±1.2 798–903 K HCl 5.6 +3.5 −2.1 34.7±3.5 828–902 K HBr 1.9 +0.3 −0.3 34±1.2 836–925 K A limited body of data is reported for k (K + C 2 H 5 Br) = 3.6 × 10 −11 cm 3 molecule −1 s −1 for the temperature range 704–733 K. These results for atomic potassium constitute a new body of absolute rate data which are compared with some previous results for reactions of atomic potassium with other reactants, and for reactions of atomic sodium, also determined by time‐resolved atomic resonance absorption spectroscopy. The data for HCl and HBr are finally compared with early estimates reported using diffusion flames.