Dielectric relaxation of lower alcohols in the whole fluid phase

摘要

Dielectric relaxation of ethanol and 1-propanol have been measured in a wide fluid phase including the supercritical condition for the first time.The results of the static permitivity epsilon(0) and the dielectric relaxation time tau_D are presented in the temperature and pressure range up to 670K and 30MPa.kirkwood's g-factor deduced from epsilon(0) suggests that the critical density.We divide the fluid phase inot four regions and discuss the dielectric relaxation mechanism by extending our model previously applied ot water K Okada et al.,J.Chem.Phys.110,3026(1999).In the vapor and low-density liquid,the dielectric relaxation is governed by binary collision of molecules.In the high-temperature liquid,the molecules that escpe form the hydrogen bond (HB) network also contribute to the relaxation,and the HB breaking is promoted by thermal excitation of the intermolecular stretchin gmodes.In the low-temperature liquid,the escape time is strongly in a more cooperative way than the intermolecular stretching vibrations.Thepresent interpretation gives a room temperature,and also provide a microscopic basis for the glass transiton scenario by Hansen et al.J.Chem.Phys.107,1086(1997).