Hindered Molecular Rotation and the Dielectric Behavior of Condensed Phases

The polarizability of a liquid or a collection of randomly oriented single crystals in which polar molecules are unable to move except to rotate from one to the other of two equilibrium orientations separated by an angle β and of potential energies whose difference is E, is α=(μ2/6kT)(−cos β)/cosh2E/2kT,where μ is dipole moment. This model accounts for the reduction of α in solids and liquids from the value μ2/3kT observed in gases, and at the same time provides for anomalous dispersion in terms of discontinuous molecular processes.