ORIENTATIONAL RELAXATION IN HYDROGEN-BONDED SYSTEMS - LIQUID WATER

A two-fractional confined rotator/extended diffusion model has been su ggested to calculate the wide-band (0 < nu/cm-1 < 1000) complex permit tivity spectra and absorption coefficient of liquid water caused by re orientations of the H2O polar molecules. The motion of water molecules coupled with 'normal' hydrogen bonds is considered from the viewpoint of the confined rotator model, while in the case of the weakened hydr ogen bonds, similar motion is described by the extended diffusion mode l. It is shown that the experimental dielectric spectra are in qualita tive agreement with the theoretical ones calculated tor liquid water. The auto-correlation functions (ACFs) of the dipole moment and angular velocity are calculated for liquid water. For the purpose of comparis on we also calculate the ACFs for one of the nonassociated polar liqui ds, CH3F. Both ACFs are interpreted in terms of the molecular models p roposed in this paper.