Exploring the Reactions of Fe+ and FeO+ with NO and NO2

Abstract

We report for the first time temperature dependences (from 300 to 600 K) of the reactions of Fe(+) and FeO(+) with NO and NO(2). Both ions react quickly with NO(2), and their rate constants have weak negative temperature dependences. The former is consistent with the calculated energy profile along the Fe(+) + NO(2) reaction coordinate. Ground state Fe(+) reacts with NO(2) to produce only FeO(+), while FeO(+) reacts with NO(2) to produce NO(+) exclusively. Certain source conditions produce excited Fe(+), as evidenced by production of primary NO(+), which is endothermic with the ground state by 0.35 eV. The room temperature rate constants are in agreement with previous values. For the reactions of Fe(+) and FeO(+) with NO, we find an upper limit of <1.0 × 10(-12) cm(3) s(-1) for both rate constants, in contrast to a previous report of a rate constant of ∼1.7 × 10(-11) cm(3) s(-1) for Fe(+) + NO. Because this is an endothermic process, the prior report interpreted the reaction as a termolecular process involving two NO molecules; instead, we show that the previous results were likely due to an NO(2) impurity. Implications for other metal cation reactions which have been speculated to occur by the termolecular mechanism are discussed.