What is the primary mover of water dynamics?

Abstract

Even today, the H-bonded cluster structure of water still stands as a major point of debate in the science of liquids. Much of this discussion is devoted to understand its dynamic nature. This has a direct impact on deciphering the many anomalies of water such as its exceptional heat capacity. Of these properties, dielectric permittivity and relaxation are of particular interest. The argument rages over whether the almost Debye-like character of the dispersion is the result of the reorientation of an apparent dipole moment of the water cluster or simply the cumulative effect of single water molecule reorientation. Furthermore, like many glass formers, it has a high frequency excess wing that does not fit into the accepted models of a single relaxation time of the main peak. Herein, we present evidence that the microscopic origins of both the excess wing and the main relaxation process of pure water are the same. The origin of these two features is explored and we suggest a new paradigm for water relaxation based on the concept of a proton cascade leading to a cluster reorientation.