Far-infrared spectra of highly viscous liquids: glycerol and triacetin (glycerol triacetate)

Far-infrared spectra in the region 25-500 cm(-1) were obtained for glycerol and triacetin (glycerol triacetate) at temperatures from 253 to 323 K. Far -infrared spectra of glycerol look more complicated in comparison with spec tra of triacetin due to the hydrogen bonding. Band fitting performed for th e frequency range 25-250 cm(-1) shows that four bands have contributed to s pectra of glycerol and triacetin in this region. The experimental results o btained for glycerol are in good agreement with normal mode: analyses perfo rmed recently for crystalline glycerol [E.J, Bermejo, A. Criado, A. de Andr ess, E, Enciso, H. Schober, Phys. Rev. B 53 (1996) 5259.] and for glycerol in the Liquid stare [T. Uchino, T. Yoke, Science 273 (1996) 480.]. The far- infrared result are compared to the low-frequency Raman spectra of the two liquids. The difference in temperature behaviour revealed from these two ki nd of spectra is explained on the basis of different temperature contributi on of relaxational and vibrational processes to the low-frequency vibration al spectra. (C) 1998 Elsevier Science B.V. All rights reserved.