Depolarized Rayleigh Spectra and Hydrogen Bonding of Liquid 1, 5- and 2, 4-Pentanediol
Low frequency depolarized light scattering (DLS) in a liquid provides information about the intrinsic anisotropy of the polari-zability tensor. In the case of small non hydrogen bonded anisotropic molecules, it has been well established, that the dynamics of molecular anisotropy is reflected in the depolarized Rayleigh spectra. In the case of liquids with strong intermolecular interactions, such as hydrogen bonding, the DLS may contain components due to a structural anisotropy induced by these interactions. Thus we have observed in 1,2,6-hexanetriol that the isolated molecule at high temperatures has a very low anisotropy in the low frequency region (~ 10 GHz). Similar observations have been reported for liquid water. Also the different dielectric relaxation behavior of five isomeric pentanediols has been related to the extent of intramolecular H-bonding. In order to examine closely these interactions, as manifested in the average molecular anisotropy, we have measured the depolarized Rayleigh spectra of 1,5- and 2,4-pentanediol in the temperature range 230 to 350K using Fabry-Perot interferometry.
KeywordsOptical Anisotropy Large Activation Energy Orientational Relaxa Intrinsic Anisotropy Dielectric Relaxation Behavior
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