Solvation and rotational relaxation of coumarin 153 in a new hydrophobic ionic liquid: An excitation wavelength dependence study

► Time-resolved fluorescence of coumarin 153 has been studied. ► Tris(pentafluoroethyl)trifluorophosphate (FAP)-based ionic liquid has been used. ► Average solvation time is found to depend on the excitation wavelengths. ►The observation is attributed to the heterogeneous nature of the ionic liquid.