Kinetics of the Homogeneous Exchange Reaction: 14–14N2+15–15N2⇋214— 15N2. Single‐Pulse Shock‐Tube Studies

The kinetics of the homogeneous exchange reaction in molecular nitrogen highly diluted in argon was studied in a single‐pulse shock tube over a wide range of temperatures, initial pressures, and compositions. The reaction order with respect to the total nitrogen, argon, and the over‐all reaction order were determined. A rate law: Rate=kb[Ar][N214]+kb[Ar ][N215], which is a sum of two parallel reactions, was found to be compatible with the experimental results kb=1013.82±0.31 exp[−(116±5)×103/RT) cc mole−1·sec−1. It was shown that the exchange reaction does not proceed via a radical chain. A mechanism based on vibrational excitation of the nitrogen molecule to a critical vibrational level as a rate determining step is proposed. A rate constant, computed from available vibrational relaxation data in nitrogen agrees very well with the observed rate constant.It was found that slight amounts of oxygen, up to O2/N2∼0.01, had very little effect on the reaction rate. In the presence of higher oxygen concentration...

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