Light emission from reaction of atomic oxygen with nitric oxide at low pressures
Abstract
The intensity Io of chemiluminescent emission by NO2 produced from the reaction of atomic oxygen with nitric oxides has been reinvestigated in the pressure range 10–250 µ Hg using a fast flow system. The equation I=Io[O][NO] was obeyed down to pressures of 60 µ Hg. At lower values the light emission became pressure-dependent. The results are explained in terms of a three-body mechanism : O + NO + M → NO†g2+ M (1a), O + NO + M → NO*2+ M (1b), NO*2+ M → NO†2+ M (2), NO*2→ NO2+hv(3), where † and * represent vibrationally and electronically excited species respectively. The quenching constant k2/k3 is calculated as 67 torr–1 and k2 is estimated as 5 × 10–11 cm3molecule–1sec–1. Consideration of these values in conjunction with the known value for the overall rate constant implies that K1bK1a. The differences between the present data and that of earlier workers are suggested as arising from the previously neglected losses of atomic oxygen as a result of rapid radial diffusion and wall recombination at low pressures.