By modeling reactions as Langevin motion along a one dimensional reaction coordinate, Hendrik Kramers was able to derive a relationship between the shape of the potential energy surface along the reaction coordinate and the transition rates of the system. The formulation relies on approximating the potential energy landscape as a series of harmonic wells. In a two state system, there will be three wells; a well for state A, an upside-down well representing the potential energy barrier, and a well for state B. 
In the overdamped (or "diffusive") regime, the transition rate from state A to B is related to the resonant frequency of the wells via
where  is the frequency of the well for state A,  is the frequency of the barrier well,  is the viscous damping,  is the energy of the top of the barrier,  is the energy of bottom of the well for state A, and  is the temperature of the system times the Boltzmann constant.
For general damping (overdamped or underdamped), there is a similar formula.