Polar solvation dynamics in the femtosecond evolution of two-dimensional Fourier transform spectra

Femtosecond two-dimensional Fourier transform (2D FT) spectra remove inhomogeneity and simultaneously provide time resolution and two dimensions (excitation, signal) of frequency resolution limited only by the sample. The time evolution of separate real and imaginary 2D FT spectra is used to study local environments around molecules in methanol. Polar solvation dynamics are extracted by comparing 2D FT spectra of structurally related dyes with and without spectral sensitivity to solvent polarity. This comparison reveals specific signatures of inertial motion and the dynamic Stokes' shift.