Cavity-modified unimolecular dissociation reactions via intramolecular vibrational energy redistribution

Abstract

While the emerging field of vibrational polariton chemistry has the potential to overcome traditional limitations of synthetic chemistry, the underlying mechanism is not yet well understood. Here, we explore how the dynamics of unimolecular dissociation reactions that are rate-limited by intramolecular vibrational energy redistribution processes can be modified inside an infrared cavity. We study a classical model of a bent triatomic molecule, where the two outer atoms are bound by anharmonic Morse potentials to the center atom. We show how energy-dependent anharmonic resonances emerge and that resonantly coupling the optical cavity to particular dynamical resonance traps can either significantly slow down or increase the intramolecular vibrational energy redistribution processes depending on the strength of vibrational momentum-momentum mode coupling, leading to altered unimolecular dissociation reaction rates. These results demonstrate that chemical reactivity can be modified inside a cavity and lay the foundation for further theoretical work toward understanding the intriguing experimental results of vibrational polariton chemistry.

Generalization of the Tavis–Cummings model for multi-level anharmonic systems

“…[25][26][27][28][29][30][31][32] The multilevel anharmonic spectrum of these vibrational modes implies that their accurate description should invoke more than two levels per emitter. Indeed, consideration of more realistic vibrational SC systems involving anharmonicities has been the subject of theoretical explorations, such as the use of single-molecule models to explain cavity-induced modifications to chemical reactivity, [33][34][35][36][37] as well as the use of many-molecule models a) Electronic mail: joelyuen@ucsd.edu; http://yuenzhougroup.ucsd.edu to explain non-linear response experiments. 28,[38][39][40][41][42][43] In particular, recent work [44][45][46][47][48][49] has elucidated novel multiphoton absorption phenomena where the TC description is insufficient, and a multilevel anharmonic spectrum of the material is essential.…”

Suppression and Enhancement of Thermal Chemical Rates in a Cavity

“…The molecule–cavity system is considered within the classical approximation, thus transforming all operators in Hamiltonians and to classical functions. A classical description of the VSC regime is not new and has been successfully applied to bulk systems described by force-field potentials and model Hamiltonians. , The cis – trans reaction rate is described with the reactive flux method for the classical rate constant − ,, where x cis is the equilibrium fraction of HONO at the cis geometry, τ̇(0) is the initial velocity of a phase-space point perpendicular to the dividing surface between reactants and products, and τ ‡ is the torsion angle corresponding to the transition state (TS) geometry. The brackets indicate the canonical ensemble average over trajectories, where we considered a temperature of 300 K throughout.…”

“…A classical description of the VSC regime is not new and has been successfully applied to bulk systems described by force-field potentials 37 and model Hamiltonians. 20,38 The cis−trans reaction rate is described with the reactive flux method for the classical rate constant [34][35][36]39,40…”

Generalized Resonance Energy Transfer Theory: Applications to Vibrational Energy Flow in Optical Cavities

“…In this sense, the thermal rate calculation proposed for VSC-catalyzed reactions and the gRET theory developed for VSC-assisted vibrational dynamics are complementary and can be integrated to yield a more complete picture. Of particular relevance is the potential application of gRET to intramolecular vibrational energy redistribution (IVR) in cavities, as exemplified by the solvated ABA model illustrated in Figure d, which has been suggested as a mechanism to understand cavity-catalyzed reactions. , …”