As shown in Fig. , the deconvoluted Pake patterns for the N-D deuterons is similar, indicating the same H-bond strength at about 30 K different temperatures. Apparently, the same HB strength is present for [TEA-d16][OMs] already at higher temperature. Such a temperature difference between differently isotopically labelled compounds has been observed of molecular liquid such as water and alcohols from high energy photon diffraction experiments. While the DQCCs are sensitive to changes present within a single cation-anion pair, we are also interested to see how isotopic substitution affects the behavior of the whole pair in the solid region. For that purpose, we addressed the dynamically heterogeneous phase being a remarkable feature of the PIL [TEA-d1][OMs] in the temperature range between 220 K and 300 K. This coincides with the differential scanning calorimetry (DSC) traces of [TEA-d1][OMs] as observed upon heating and cooling. We observed the melting peak at 306 K and a cold crystallization peak at 240 K. The 2 H spectra measured between the melting and the crystallisation temperatures can be simulated by the superposition of both line shapes.