Suppression of reaction rates via photon emission under laser or dark cavity coupling: O 2 + 2 NO → 2 NO 2 as an example

Abstract In this work, we demonstrate the suppression of the reaction rate by a dark cavity. This is an extension of the previously studied suppression of electronic transitions in a resonant tunneling diode, which involves a symmetric double-barrier potential, via a photon-emission mechanism. Our present calculations reveal two asymmetric potential barriers along the studied reaction pathway from O 2 + 2NO to 2NO 2 . A two-step approach is taken. In the first step, O 2 collides with NO to produce NO 3 . In the second step, NO 3 interacts with another NO molecule to produce the final products, 2NO 2 . The resonances of the activated complex are calculated by imposing outgoing boundary conditions using the smooth exterior scaling approach, which suppresses the exponential growth of the resonance wavefunctions induced by these boundary conditions. These resonances are then used as the basis set for calculating the reaction rate. At sufficiently high temperature, where the reaction proceeds without tunneling, the rate is governed by the transition-state (TS) resonance located at the top of the potential barrier. The dark cavity induces coupling between this TS resonance and a lower-lying resonance located inside the potential well between the two barriers via the emission of a single photon. This coupling suppresses the reaction rate for a single molecule in the cavity as well as for many non-interacting molecules within the cavity.