8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Tue 611:23-14:00P2.49Intermolecular polarizability dynamics of sugar aqueoussolutions: molecular dynamics simulations anddepolarized light scattering experimentsLaura Lupi, 1 Lucia Comez, 1 Marco Paolantoni, 2 Branka M. Ladaniy, 3 and DanieleFioretto 11 Department of Physics, University of Perugia, Via A. Pascoli, 06123, Perugia,Italy2 Department of Chemistry, University of Perugia, Perugia, Italy3 Colorado State University, Fort Collins, Ud States of AmA molecular dynamics simulation has been performed to investigate the dynamics of polarizabilityanisotropy of trehalose-water and glucose-water solutions. The time correlation functions (TCF)of the collective polarizability was usefully separated into three terms, arising from the solute, thesolvent and the cross term between the two. The analysis of the contribution from water givesdirect evidence of the existence of two distinct relaxation processes at picoseconds timescales,attributed to the dynamics of bulk and hydration water molecules, respectively. A retardationfactor of 5-6 is found for hydration water with respect to bulk, in good agreement with the resultsobtained by depolarized light scattering experiments [1]. The direct comparison of the calculatedRaman spectra profiles with the experimental ones at all compositions strongly supports theanalysis previously performed on experimental data, where solute and water contributions weresupposed to be spectrally separated. Moreover, the calculated average number of water moleculesin the first hydration shell of the sugar, as a function of composition, shows a very good agreementwith the values independently obtained by experimental spectra.[1] M. Paolantoni, L Comez, M. E. Gallina, P. Sassi, F. Scarponi, D. Fioretto, A. Morresi,J. Phys. Chem. B 113, 7874-7878 (2009).49