Rovibrational excitation of nitric oxide in the reaction of oxygen with metastable atomic nitrogen

Abstract

The dynamics of the reactions of N({sup 2}D,{sup 2}P) with O{sub 2} have been investigated by observing the initial vibrational-state population distributions of NO(X{sup 2}II) formed in the interaction of oxygen and discharge-excited nitrogen in a cryogenically pumped, low-pressure reaction volume. Infrared chemiluminescence from vibrationally and rotationally excited NO(v = 1-14) was observed in the 5-7-{mu}m spectral region, and spectral data were analyzed to obtain NO(v,J) number densities. The results show multimodal vibrational and rotational distributions, indicative of several concurrent processes. In particular, extensive rotational excitation is evident in several vibrational levels of NO, resulting in sharply peaked R-branch band heads characteristic of J {ge} 80. Surprisal analysis was applied to the data to infer the contributions of the various reaction pathways. This analysis indicates that all the possible reaction pathways for producing NO(X{sup 2}II), some of which leads to formation of metastable atomic oxygen, occur with significant probability. The results are discussed in terms of their implications for the detailed collisional dynamics of the reactions and their relevance to the study of upper atmospheric auroral chemistry.