On the vibrational transition selection rules for the centrosymmetric hydrogen-bonded dimeric systems

Effects of strong inter-hydrogen bond dynamical couplings in the polarized IR spectra of adipic acid crystals

“…The forbidden transition in the IR may, however, become spectrally activated via the vibronic promotion mechanism, which is a reverse of the familiar Herzberg-Teller mechanism [18] from the electronic spectroscopy of aromatic hydrocarbon molecules. Therefore, the sub-band connected with the forbidden vibrational transition may appear in the spectra of centrosymmetric hydrogen bond dimers [18]. It contributes with the F À statistical weight.…”

“…This mechanism, acting together with the selection rule breaking mechanism for IR transitions in centrosymmetric hydrogen bond dimers [18] is the reason for the appearance of the two-branch fine structure pattern of the m O-H and m O-D bands. Hence an identical linear dichroic effect, i.e., a constant vibrational transition moment direction in the whole frequency range of each band can be expected [18].…”

“…It can be satisfactorily reproduced quantitatively by the so-called ''plus" band [7,45] contributing with the F + statistical weight. In this case both component transitions contributing at the generation of each analyzed band should exhibit identical polarization properties [18]. Such The above presented idea was also incorporated in the past to the ''relaxation" theory in order to interpret quantitatively the IR spectra of the hydrogen bond in h 10 and d 2 adipic acid crystals [26].…”

“…doi:10.1016/j.chemphys.2009.09.005 mechanisms of dynamical co-operative interactions in hydrogen bond systems [16,17] and the mechanism of vibrational selection rule breaking in IR spectra of centrosymmetric hydrogen bond dimers [18]. Both mechanisms are basically of a vibronic nature [16][17][18]. Therefore, the quantitative interpretation of the IR spectra of even such simple hydrogen bond aggregates like cyclic, centrosymmetric dimers (found for instance in associated carboxyl groups, (COOH) 2 ), requires solution of non-standard problems.…”

Theoretical model of infrared spectra of hydrogen bonds in molecular crystals of 2-thiopheneacetic acid: Fermi resonance and Davdov coupling effects.

“…This parameter is similar to the breaking of the IR selection rule forbidding the Ag transition in cyclic dimers of carboxylic acids [32]. The spectral densities are computed by Eq.…”