Figure 15: The theoretically derived band contours calculated in terms of the “strong-coupling” theory in the limits of the two different vibrational exciton coupling mechanisms involving the cyclic dimer hydrogen bonds, that is, “side-to-side” (SS) and “tail-to-head” (TH). (a) The SS coupling mechanism. (b) The TH coupling mechanism. (I) The “minus” band. (II) The “plus” band. (III) Superposition of the spectra I and II, each taken with its appropriate individual statistical weight parameter, and . In both mechanism cases, the same coupling parameter value system was used for calculations: = 0.7, = 0.7, = −0.2, = 1.0, = 0.2, Ω_{O⋯O} = 100 cm^{−1}. The transition frequencies are in the ω _{O⋯O} vibrational quantum units, and the transition frequencies are expressed with respect to the gravity center of the hypothetical spectrum of a monomeric hydrogen bond in the cyclic deuterium bond dimer. Transition intensities are in arbitrary units.