Reactions of 1 D and 3 P oxygen atoms with cyanogen by flash photolysis

Abstract

The reactions of ground-state and first-excited-state oxygen atoms with cyanogen have been investigated using the technique of flash photolysis and kinetic spectroscopy. In experiments using ozone+cyanogen mixtures under conditions where only the ozone is decomposed by the photolytic flash to give O¹D, it was possible to detect absorption due to CN and NCO together with other transient spectra in the regions 2807, 3290, 3920 and 4265 Å. From the kinetic evidence described in this work together with spectroscopic data obtained elsewhere these latter spectra would appear to be due to the free NCN radical. No transient species were observed during the photolysis of nitrogen dioxide+cyanogen mixtures where the reaction involved is that between ground-state (³P) oxygen atoms and cyanogen. Investigations were also carried out on cyanogen+oxygen mixtures using an annular spectrosil flash tube-reaction vessel assembly; the cyanogen was dissociated to a considerable extent and reactions between free CN radicals and molecular oxygen were studied. From the results obtained it is concluded that ground-state oxygen atoms do not react with cyanogen to any appreciable extent at room temperature, whereas O¹D atoms react rapidly, O¹D+C₂N₂→NCO + CN. The reaction between free CN radicals and molecular oxygen is also fast, again leading to the formation of NCO according to CN+O₂→NCO+O(³P). Subsequent reactions leading to the production of NCN radicals are discussed.