A Reaction Kinetic Model for Vacuum-Field Catalysis Based on Vibrational Light-Matter Coupling

Since conventional catalysts are materials-based, they are effective only for particular chemical reactions. Recent studies suggest that vacuum-field catalysis (or cavity catalysis) based on vibrational light-matter coupling can boost reactions without the above constraint. Herein, we propose a reaction kinetic model for such vacuum-field-catalyzed reactions. Vibrational light-matter coupling is an interaction in which a molecular vibration and infrared (IR) vacuum field are coupled in resonance, consequently creating a pair of Rabi-split vibro-polaritonic states. Our kinetic model hypothesizes that vibrational light-matter coupling reshapes the reaction potential surface, thereby changing its reaction barrier height. We translate such a qualitative picture into two kinds of analytical equations derived from the Arrhenius and Eyring–Polanyi theories: both the equations are obtained as a function of the coupling ratio Ω_R/2ω₀ of vibro-polaritons (Ω_R: Rabi frequency between a pair of vibro-polaritons, ω₀: vibrational frequency of reactants), indicating that Ω_R/2ω₀ is a decisive quantity to define the catalytic activity of vacuum-field catalysis. Our numerical calculation shows that when Ω_R/2ω₀ ≥ 0.1, reactions may be accelerated by several orders of magnitude. Most importantly, our kinetic model can account well for rate enhancements ranging from ~10⁰ to ~10⁴ observed for vacuum-field-catalyzed reactions. We expect that our findings will bring fresh perspectives not only to chemistry but also to the broad fields of science and technology.