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Two-dimensional infrared spectroscopy has reported highly delocalized in-plane base vibrations in the fingerprint region of nucleotide monophosphates, suggesting the involvement of base pair C= O and C= C ring bonds and considerable interaction between C= O bond stretches. The high delocalization results in congested vibrational spectra, which complicates the assignment of the peaks. This congestion also extends to Watson–Crick base pairs. We applied in this work the characterization of normal mode procedure, a special feature of our local mode analysis, and could for the first time identify the C= O and C= C bonds being engaged in base pair coupling and quantify their contribution to each of the delocalized fingerprint vibration. In addition, a detailed and quantitative description of the hydrogen bonds involved in the Watson–Crick base pairs was provided. Based on the results of this study, we developed …