  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 (IVR) can be modified inside an infrared
optical 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
coupled to a harmonic bending mode. We show that an optical cavity resonantly
coupled to particular anharmonic vibrational modes can interfere with IVR and
alter unimolecular dissociation reaction rates when the cavity mode acts as a
reservoir for vibrational energy. We find a strong dependence on the initial
state of the cavity and molecule. In particular, when the cavity is initially
empty, the dissociation rate decreases, while when the cavity is initially
hotter than the molecule, the cavity can instead accelerate the reaction rate.
These results lay the foundation for further theoretical work toward
understanding the intriguing experimental results of vibrational polaritonic
chemistry within the context of IVR.
