The Ohio State University

Over thirty years after Fenimore observed an alternative formation pathway to the thermal (Zeldovich) mechanism for NO formation; its details are still not adequately understood.  For many years, the CH + N₂ = HCN + N reaction was widely considered as the initiating reaction to the "prompt NO" formation pathway, which has been well supported by existing NO measurements.  However, in recent years the products of the CH + N₂ reaction have come under question, with new high-level ab initio computations indicating that the products of that reaction are NCN + H.  In this talk, I will review some of the more recent work in this area and discuss experimental and modeling work that was conducted at the Naval Research Laboratory in Washington, DC, in which the CH + N₂ reaction and its products were systematically studied.  In particular, I will discuss experimental measurements of CH, NCN, and NO that were obtained by laser-induced fluorescence (LIF) that provided the first mechanistic study indicating that the CH + N₂ reaction does proceed through the NCN pathway in C₁-C₄ hydrocarbon flames.  I will also discuss modifications to existing chemical kinetic mechanisms that can adequately capture the modified formation chemistry.  Finally, some interesting results in C₂-C₄ alkane flames will be discussed which indicate that additional prompt NO precursors in addition to CH are responsible for the formation of NCN and the subsequent NO production in higher hydrocarbon flames.