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 th is wide range of solvent viscosities, from the glass transition to bey ond the melting point, the mean relaxation times for the two technique s which monitor dipolar orientation are identical within our resolutio n. For two characteristic decay traces recorded on the time scales of 10 ns and 1 s we compare the observed Stokes-shift dynamics with vario us theoretical approaches. The decay pattern is reproduced by the dipo lar dynamic-mean-spherical-approximation, whereas the absolute time sc ale of the solvation is mapped by the dielectric polarization itself. For the solvent under study we find almost perfect agreement between e xperiment and the dipolar dMSA theory if the time scale of the predict ed curve is rescaled by a factor of (epsilon(infinity)/epsilon(s))(1/2 ).