Exploring quantum tunneling in heavy atom reactions using a rigorous theoretical approach to the dynamics. Formation of NO + O from the N + O2 atmospheric reaction

Abstract

This theoretical work is centered on the rigorous study of the importance of quantum effects (tunneling and over the barrier reflection (non-classical reflection)) in heavy atom reactions, considering in this case the elementary gas phase reaction N + O2(v0=0, j0=1) ⟶ NO + O, which is relevant, e.g., in the oxidation mechanism of nitrogen (Zeldovich’s mechanism) and air cold plasmas. We have examined the quantum and classical reaction probability, cross section (Ecol: 0.200-0.651 eV) and rate constant (T: 200-1000 K) of this reaction. To do this, we have applied the close-coupling time-dependent real wave packet (CC-TDRWP) method and the quasiclassical trajectory (QCT) method. Even though we are considering a heavy-heavy-heavy atom reactive system, quantum effects are playing a notable role in the low energy region. Thus, for the cross section they are relevant in the 0.334-0.381 eV Ecol interval, while below 0.334 eV reactivity is only possible by tunneling (the minimum energy required for N + O2(v0=0, j0=1) to overcome the barrier is 0.299 eV). Furthermore, quantum effects are also evident in the rate constant for temperatures between 200 and 500 K. Lastly, we have also made known the limited degree of validity of the J-shifting approximation in the title reaction. From what we know, this work corresponds to the most rigorous theoretical study carried out so far on quantum effects and reactivity for reactions involving only heavy atoms. We expect that it will encourage more investigations of this type in the future, since it is an interesting problem that has been little explored to date.