Vibrational energy transfer of very highly vibrationally excited NO

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Abstract
The dependence of vibrational energy transfer on vibrational excitation has been studied using the stimulated emission pumping technique to efficiently prepare a large range of specific vibrational states of the nitric oxide molecule in its ground electronic state. Laser induced fluorescence was used to detect collisionally relaxed NO. The self‐relaxation rate constants of NO(v≫1) were up to 200 times larger than that of NO(v=1). Multiquantum relaxation was found to be important at high energy and was quantified at 3.8 eV. Self‐relaxation rate constants of 15N18O as well as 14N16O were measured and a large isotope effect was observed. Relaxation of NO(v‘=22) with H2 was also investigated. Theoretical explanations of our experimental results were attempted and it is shown that at vibrational energy up to ≊3 eV the qualitative trends observed in these experiments such as the mass effect and the multiquantum relaxation can be explained by Schwartz–Slawsky–Herzfeld theory. A simple explanation of the anomalously high NO self‐relaxation rate is given. The large acceleration of the vibrational relaxation rate above 3.0 eV is coincident with the energetic onset of high energy (NO)2 isomer complexes. More theoretical and experimental work is needed to explain the quantitative aspects of these observations.