Dynamics of solvation in supercooled liquids confined to the pores of sol-gel glasses

We have measured the solvation dynamics of the probe molecule quinoxaline in a glass-forming solvent, 2-methyltetrahydrofuran, geometrically confined to the pores of sol-gel glasses having nominal pore diameters (Formula presented) nm. Within the time range (Formula presented) the (Formula presented) process and a second extremely slow process are observed. On the basis of emission spectra, the latter relaxation is assigned to a surface layer with strongly frustrated dynamics, opposed to the picture of a certain fraction of pores entirely filled with liquid of reduced molecular mobility. According to the Stokes-shift results for porous samples, the thickness of this surface layer increases significantly with (Formula presented) for the system under study. The results are compared with solvation dynamic experiments for the bulk solvent and with dielectric relaxation measurements.