NOxCatalyzed Pathway of Stratospheric Ozone Depletion: A Coupled Cluster Investigation

We report a theoretical investigation on the NOxcatalyzed pathways of stratospheric ozone depletion using highly accurate coupled cluster methods. These catalytic reactions represent a great challenge to state-of-the-art ab initiomethods, while their mechanisms remain unclear to both experimentalists and theoreticians. In this work, we have used the so-called “gold standard of quantum chemistry,” the CCSD(T) method, to identify the saddle points on NOx-based reaction pathways of ozone hole formation. Energies of the saddle points are calculated using the multireference variants of coupled cluster methods. The calculated activation energies and rate constants show good agreement with available experimental results. Tropospheric precursors to stratospheric NOxradicals have been identified, and their potential importance in stratospheric chemistry has been discussed. Our calculations resolve previous conflicts between ab initioand experimental results for a trans nitro peroxide intermediate, in the NOxcatalyzed pathway of ozone depletion.