The state ψ G (q; q i ) corresponds to the displaced ground state wavefunction of the harmonized reactant mode of frequency ω R and width σ ≡ (ℏ/µω R ) 1/2 . The average initial total energy ⟨H⟩ Ψ0 ≡ ⟨Ψ 0 |H|Ψ 0 ⟩ depends on the displacement q i of the wavepacket. We consider the cavity to have no photons initially and hence the state ϕ 0 (x c ) is taken to be the ground harmonic eigenstate of the cavity mode with frequency ω c . However, in order to ensure a zero-photon initial cavity state for finite coupling a more appropriate choice is