Extracting the ∆𝜈̅ 𝐻𝐵 values for head-on or side-on HBs, we can quantify the distance-dependence of ∆𝜈̅ 𝐻𝐵 . We combined the data sets for water and methanol HBs, and we found that head-on HBs (θ = 175°) demonstrate an asymptotic trend (Fig. ) which decays from ~ 50 cm -1 at 2.5 Å to ~ 5 cm -1 at 5.0 Å according to a power law