SOLVATION DYNAMICS AND THE DIELECTRIC RESPONSE IN A GLASS-FORMING SOLVENT - FROM PICOSECONDS TO SECONDS

We have measured the response times of solvation dynamics in the range 100 ps to 100 s and the dielectric relaxation covering 10 decades in frequency for the glass-forming solvent 2-methyltetrahydrofuran. In this wide range of solvent viscosities, from the glass transition to beyond the melting point, the mean relaxation times for the two techniques which monitor dipolar orientation are identical within our resolution. For two characteristic decay traces recorded on the time scales of 10 ns and 1 s we compare the observed Stokes-shift dynamics with various theoretical approaches. The decay pattern is reproduced by the dipolar dynamic-mean-spherical-approximation, whereas the absolute time scale of the solvation is mapped by the dielectric polarization itself. For the solvent under study we find almost perfect agreement between experiment and the dipolar dMSA theory if the time scale of the predicted curve is rescaled by a factor of (epsilon(infinity)/epsilon(s))(1/2).