Pressure dependence of solvation dynamics of coumarin 480 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.