Determination of absolute rate data for the reactions of atomic sodium, Na(3²S1/2), with CH₃F, CH₃Cl, CH₃Br, HCl, and HBr as a function of temperature by time‐resolved atomic resonance spectroscopy

We present a kinetic study of the reactions of ground‐state sodium atoms with the molecules CH 3 F, CH 3 Cl, CH 3 Br, HCl, and HBr at elevated temperatures (537–966 K). Na(3 2 S 1/2 ) was generated by the pulsed irradiation of various sodium halide vapors and monitored by time‐resolved atomic resonance absorption of the unresolved D‐lines at λ = 589 nm [Na(3 2 P J ) ← Na(3 2 S 1/2 )] in the “single‐shot mode.” The photoelectric signals were amplified without distortion, captured, and digitized in a transient recorder interfaced to a microcomputer for data analysis. Absolute second‐order rate constants were measured at various temperatures in each case, yielding the following Arrhenius parameters ( k RX = A exp(– E / RT ), errors 1σ): magnified image which constitute, to the best of our knowledge, the first direct measurements of these quantities. The reaction between Na and HBr demonstrated anomalous behaviour which is discussed in terms of potential surfaces that have been calculated previously for this type of collisional process. The data are compared with analogous results for Na + CF 4 , CF 3 Cl, and CF 3 Br and with single‐temperature measurements on diffusion flames.