RECONSTRUCTING THE SOLVATION TIME-CORRELATION FUNCTION FROM THE TIME-DEPENDENT FLUORESCENCE STOKES SHIFT

A new method is presented to obtain the solvation time correlation fun ction from the time dependence of the fluorescence Stokes shift. The f luorescence band is reconstructed by using the steady-state fluorescen ce band and the time profiles of the fluorescence collected at some di screte values of the wavenumber nu. The time profiles are described as a sum of three exponentials. The time constants and amplitudes for th e discrete values of nu are used to generate a crude approximation to the true band at time t. A procedure is given to refine the crude band and to obtain the band at any time between the preparation of the flu orescent solute and the time at which its solvation has reached the fi nal stage. The method produces accurate, method-independent time-resol ved fluorescence spectra and solvation time correlation functions. In this paper it is applied to the excited state kinetics of 4-aminophtha limide in tetrahydrofuran and n-undecanol.