Ultralow-Temperature Kinetics of CH(X²Π) Reactions:  Rate Coefficients for Reactions with O₂ and NO (T = 13−708 K), and with NH₃ (T = 23−295 K)

The pulsed laser photolysis (PLP), laser-induced fluorescence (LIF) technique for the study of the kinetics of free-radical reactions is applied to reactions of CH radicals both in the ultralow-temperature environment of a Cinétique de Réaction en Ecoulement Supersonique Uniforme (CRESU) apparatus, as well as in a conventional heated cell. The combined techniques provide kinetic data over an extremely wide temperature range. Rate coefficients are reported for the reactions of CH with O 2 ( T = 13−708 K), NO ( T = 13−708 K), and NH 3 ( T = 23−295 K). All three reactions remain very rapid down to the lowest temperatures at which measurements were made and display differing temperature dependences. The results are discussed in the light of previous work on these systems and of the reaction mechanisms.