Abstract
Two types of spectroscopic measurements were carried out to determine the effect of microscopic viscosity on molecular dynamics in saccharide aqueous solutions. Femtosecond pump-probe (PP) spectroscopy was carried out to monitor diffusional phenyl ring rotation of malachite green (MG) molecule which occurred in a time scale of picoseconds. Fluorescence correlation spectroscopy (FCS) was also carried out to monitor the translational diffusion of rhodamine 6G (R6G) molecules in the vicinity of a focusing point of an objective lens, which occurred in a time scale of sub-milliseconds. The PP signal exhibited multi-exponential decay, indicating a microscopic inhomogeneity of the viscosity. On the other hand, time correlation function obtained by FCS measurement exhibited single exponential decay, indicating that the inhomogeneity of the saccharide solution was averaged out and has disappeared in the sub-millisecond time scale.
