LDS-750 as a probe of solvation dynamics: a femtosecond time-resolved fluorescence study in liquid aniline

The dynamics of the fluorescence Stokes shift of the styryl dye LDS-750 hav e been measured in liquid aniline with sub-100 fs time resolution. The shap e of the time-resolved spectra are time dependent, which is not consistent with the predictions of a solvation dynamics mechanism. However, the measur ed spectral shift correlation function is reasonably well described by the dynamical mean spherical approximation model of solvation dynamics. It is s uggested that these observations are consistent if solvent dynamics is the rate controlling process in both solvation of the increased dipole moment o f the excited state of LDS-750 and the stabilisation of a distribution of s olute conformers in the excited state. (C) 1999 Elsevier Science B.V. All r ights reserved.