  We present a microscopic theory that aims to explain the vibrational strong
coupling (VSC) modified reaction rate constant. The analytic theory is based on
a mechanistic conjecture that cavity modes promote the transition from the
ground state to the vibrational excited state of the reactant, which is the
rate-limiting step of the reaction. The theory explains the observed resonance
effect at the normal incident angle. Assuming the coherent vibrational energy
transfer picture, the theory can also explain the collective effect and makes
several predictions that are experimentally verifiable.
