The Structure of Liquid Water Emerging from the Vibrational Spectroscopy: Interpretation with QED Theory
De Ninno A1*, Del Giudice E2, Gamberale L3, Congiu Castellano A4
1C.R. ENEA Frascati Department UTAPRAD-DIM, 00044, Italy
2Retired Scientist, Milano, Italy – deceased
3MOSE srl, Milano, Italy
4Department of Physics, Sapienza University of Rome, 00185, Italy
*Correspondence E-mail: antonella.deninno@enea.it
Key Words: Liquid water, Vibrational spectroscopy, Two-level system, QED
Received Oct 10th, 2013; Accepted Dec 28th, 2013; Published Feb 5th, 2014; Available online March 10th, 2014
Abstract
We report an analysis of the stretching peak appearing in the IR experimental spectra of liquid water. In the literature, ATR-IR spectroscopic measurements were repeatedly performed in a wide range of temperature and gave rise to a lively debate among scientists. In particular a two components model related to H-bond complexes of different strength have been proposed in order to justify the existence of two types of molecules as it appears from the spectroscopic data. At the opposite, Molecular Dynamics simulations support a multistate (continuum) system of H-bond having different strength giving rise to a (locally) tetrahedral description of liquid water. We will show that liquid water is a quantum two-level system according to the predictions of Quantum Electrodynamics (QED) and that several features (the asymmetric band profile, the existence of an isosbestic point and the modifications of the vibrational stretching band with the temperature) cannot be fully justified in the realm of a classical picture. In particular the differences of energy and entropy between the two phases are estimated from the experimental data and compared with the prediction of QED showing a remarkable agreement. The behaviour of water near hydrophilic surfaces is also discussed and several feature of the so-called “Exclusion Zone” observed by several authors are evaluated according to the two level system model.