Kinetics of OH Radicals as Determined by Their Absorption Spectrum I. The Electric Discharge Through Water Vapor

Abstract

(1) The order of the reaction causing the rapid disappearance of OH radicals after interrupting an electric discharge through H₂O vapor is measured by photometry of absorption spectra taken in snapshots. (2) These spectra are taken in time intervals of a few tenths of a second with a 21‐foot grating and rotating interrupter and sector. (3) Relative concentrations of OH radicals are derived by comparing intensities of rotational lines within one branch of the 0→0 band of OH, the relative intensities being given by the theory of Hill and Van Vleck. (4) The decay of OH with time for various H₂O pressures and addition of He is given in diagrams and a table of rate constants. (5) A discussion of the kinetics leads to triple collisions consuming OH. (6) KCl covering the surface of the absorption tube materially increases the rate of the reaction. (7) The absorption spectrum of H₂O₂ investigated simultaneously showed that no appreciable H₂O₂ is formed in the reaction. (8) In the processes consuming OH radicals after interrupting the discharge through H₂O vapor in clean glass tubes, the triple collision H+OH+M→H₂O+M plays a predominant part.