Pressure dependence of solvation dynamics of coumarin in ethanol

The effect of the pressure on the solvation dynamics of coumarin 480 in ethanol has been studied by means of time-resolved emission using the time-correlated single-photon-counting technique with 20-ps resolution. The solvation dynamics slow with pressure. The pressure was varied from atmospheric pressure to about 1.8 GPa, the liquid-solid phase transition. At low pressures, < 0.5 GPa. the solvation correlation function is nearly exponential, whereas, at pressures higher than about 0.5 GPa, it is nonexponential and can be fitted to a biexponential function whose short component is about 110 ps at pressures above 1 GPa. In the solid phase, solvation dynamics occurs at a relatively fast rate, similar to the liquid phase and at about the same pressure.