Is quenching of electronically excited NO2 by N2 an important atmospheric source of N2O?

Abstract

Context Abstract: The atmospheric budget of N2O, a greenhouse gas and the dominant source of total reactive nitrogen to the stratosphere, remains a controversial subject. Gas-phase atmospheric chemical sources of N2O are not well documented, but studies of atmospheric N2O samples show a mass-independent heavy oxygen isotope enrichment which is suggestive of the existence of missing in situ sources or sinks. We have studied N2O production from the reaction of electronically excited NO2 with N2. Contrary to earlier findings, our results show that this process is an insignificant source of atmospheric N2O.Main Abstract: Production of N2O as a product of the collisional deactivation of electronically excited NO2 by N2 has been investigated with the goal of establishing the importance of this process in the atmospheric N2O budget. The experimental approach minimizes potential interferences from heterogeneous reactions, multiphoton processes, and self-quenching. At the 95% confidence limit, we find that the quantum yield for production of N2O from 488 nm photolysis of 60 Torr of 0.1% NO2 in N2 is less than 4×10−8, i.e., at least 10,000 times smaller than a previously published value; this result suggests that quenching of electronically excited NO2 by N2 is unimportant as a source of atmospheric N2O.