Hydrogen bonds tunneling dynamics

Saykally R J and Blake G A 1993 Molecular-interactions and hydrogen-bond tunneling dynamics—some new perspectives Science 259 1570-5... 

Besides the peaks of the local proton modes typical for hydrogen bond, a sharp peak at 28 meV was observed in KDP [34] and attracted much attention [34,38,39]. This peak exists in DKDP at somewhat higher frequency its intensity decreases in both crystals and its width decreases upon the transition from the FE to the PE phase, without any softening of its frequency [38]. Hence, it is concluded that this mode is connected with the phase transition dynamics, i.e., coupled to the polarization fluctuations. This mode is not the tunneling mode or any local mode of proton or deuteron, but rather some collective optical mode of the lattice that involves substantial proton or deuteron displacement. It has been suggested [38] that this mode corresponds to the mode that has a peak at about 200 cm (25 meV) in Raman scattering and infrared reflectivity spectra, and that it is coupled to the soft mode and usually... 

As an example, we consider H NMR measurements on a single crystal of benzoic acid [ 14], carried out to investigate tunnelling dynamics in hydrogen bonded carboxylic acid dimers. 

However, the model by Stasyuk et al. [135] described in Section II.A is more attractive because it allows an estimation of the frequency of coherent orientational tunnel transitions taking into account both the proton dynamics of the hydrogen bonds and the reorientational processes of A H groups. Let us... 

Thus starting from the simplest pseudo-spin model of proton dynamics in the hydrogen bond, we have studied a possibility of spontaneous tunnel oscillations of the polarization of a short hydrogen-bonded chain. The phenomenon can be affected by two reasons (a) the coherent motion of protons along the hydrogen bonds and (b) the coherent motion of protons around heavy backbone atoms. 

---