Measurement of absolute rate data for the reaction of atomic potassium, K(4 2S1/2), with CF3Cl, CF2Cl2, CFCl3, CF3Br and SF6 as a function of temperature by time-resolved atomic resonance absorption spectroscopy at λ= 404 nm [K(5 2PJ)â†� K(4 2S1/2)]

Abstract

We present a kinetic study of the reactions of atomic potassium in its electronic ground state, K(4²S_1/2), with the molecules CF₃Cl, CF₂Cl₂, CFCl₃, CF₃Br and SF₆. Atomic potassium was generated by pulsed irradiation of potassium halide vapour at elevated temperatures and monitored in the ‘single-shot mode’ by time-resolved atomic resonance absorption using the Rydberg doublet at λ= 404 nm [K(5 ²P_J)â†� K(4 ²S_1/2)]. Absolute rate constants for reaction with these molecules were determined as a function of temperature yielding the following Arrhenius parameters (errors 1σ): [graphic omitted]. CF₄ exhibited anomalous kinetic behaviour. These results represent the first kinetic measurements, relative or absolute, for these fundamental reactions of atomic potassium. This new set of absolute rate data are compared with analogous results reported hitherto for atomic sodium, Na(3 ²S_1/2), both alkali-metal atoms exhibiting rapid reactions characterised by small energy barriers and being highly exothermic in character.