The vibronic coupling of the heavy atoms with the protons is prominent in most hydrogen bonded systems such as protonated water, protein analogues, 82 crystal hydrates and even other molecular crystals. Using PI simulations on a single Zundel ion, Benoit et al. reported the dependence of the proton transfer on the distance between the oxygen atoms. A large separation leads to the proton being localized on one water separated by a large barrier. On reducing the separation to ultra small values, the two peaks merge into one broad peak corresponding to a single potential well. Similar effects have also been observed in molecular dynamics simulations of various crystal hydrates. This dependence in TPA is illustrated by computing the joint probability distribution as a function of the proton transfer coordinates (δ 1,2 ) and its heavy atom separation (d O-O ), resulting in banana-shaped free energy profiles (Figure ). Careful inspection of the free energy profiles obtained from the BOMD simulations at 300 K (Figure Upon turning on the NQE, we observe an asymmetric banana-shaped free energy profile We further note that occurrence of proton transfer events at 70 K is in accordance with the experimental observations where the order disorder transition sets in at around 80 K. The free energy difference between the two minima is about 13 meV. The asymmetric nature of the FES, as discussed earlier, can be attributed to the crystal field effect where the L and R tautomers are not degenerate. At 300 K the difference between these two minima increases