where H is the hydrogen atom, P is the number of beads in the ring polymer, r H i is the position of the H-atom in the i th bead of the proton ring polymer and r H c is the position of the centroid of the proton ring polymer (r H c = 1 changes sign there is a peak/enhancement of r G (Figure ) suggesting that the quantum fluctuations is delocalizing the proton that is being transferred thereby resulting in an enhancement of its de Broglie's wavelength, a consequence of which is that the proton is tunnelled from one potential well to another through a barrier. In contrast, at T=300 K (Figure (b)), we do not observe any enhancement of r G when a proton transfer event is occurring. that at T=70 K, there is a large spread of r G at around δ c 1,2 =0.00 (Figure (a)) while the spread is uniform for T=300 K (Figure ). Analysing the contributions from the parallel and perpendicular components of r G , we note that these enhancements at 70 K are due to enhancements observed in r ∥ G (Figures ) and (e)), thereby further verifying that at 70 K, it is more likely that the proton transfer occurs through tunnelling while at 300 K the thermal activation seems more important. However, we would like to note that since these proton transfers are rare events making quantitative statements of the relative role of activated hopping versus tunneling cannot be currently made.