where the first two terms describe a molecular system in terms of a reaction coordinate R, with a corresponding kinetic energy operator TR , and E g (R) = ⟨ψ g | Ĥel |ψ g ⟩ is the ground state potential energy surface for the reaction coordinate R, with and a molecular ground state permanent dipole µ gg (R) = ⟨ψ g |μ|ψ g ⟩, see Sec. 2.1. Further, E g (R) takes the form of a harmonic potential near the reactant well R 0 , where E g (R) ≈ 1 2 ω 2 0 (R -R 0 ) 2 and ω 0 is the reactant well frequency. Similarly, near the transition state configuration (R = R ‡ ), E g (R) takes the form of a inverted harmonic potential,