Reactions forming electronically-excited free radicals. Part 1.—Ground-state reactions involving NF2 and NF radicals

Abstract

Atomic resonance absorption in the far vacuum ultraviolet and atomic resonance fluorescence have been used to investigate the kinetics of primary and secondary processes in the overall reaction of H ²S atoms with NF₂ radicals from 298 to 550 K. Rate constants for the following elementary reactions have been determined directly [k²⁹⁸/cm³ molecule^–1 s^–1(1 σ)]: H + NF₂ [graphic omitted] HF + NF; k₁=(1.5 ± 0.2)× 10^–11; O + NF₂ [graphic omitted] NF + FO; k₅=(1.8 ± 0.9)× 10^–12; N + NF₂ [graphic omitted] NF + NF; k₈=(3.0 ± 1.2)× 10^–12.

The overall H + NF₂ reactive system, containing H₂, is characterised as a self-propagating chain reaction, in which the chain carriers are H, NF and F. Ground-state N ⁴S atoms are formed by the reaction H + NF, although these atoms play only a minor role in propagating the overall H + NF₂ chain reaction. Computer modelling of the H and N atom profiles was used to obtain values for k₄ and k₂: H + NF [graphic omitted] HF + N; k₄=(2.5 ± 0.5)× 10^–13; NF + NF [graphic omitted] N₂+ 2F; k₂=(7.0 ± 3.5)× 10^–11. Thus, the predominant decay channel for NF radicals is through rapid bimolecular disproportionation to give N₂+ 2F.