View of the experimental setup. From back to front: hand-screw pump, fluid separator, mechanical holder connecting the high-pressure steel tubing to the silica micro-capillary, and the inverted microscope with a slide holding the micro-capillary.
Recovery of the fluorescence intensity, I (counts/second), of Coumarin 1 (1.3 × 10−3 M) in PPG 4000 M as a function of time t: (a) P = 1500 bar, (b) P = 2500 bar. The peaks correspond to the recovered fluorescence intensity when the reading beam is illuminating the sample. The solid lines are a fit to Eq. (2) . Measurements were performed at room temperature T = 20 °C.
Ratio between the characteristic diffusive times, τ Rad/τ Diff, as a function of pressure P. τ Rad is the characteristic time obtained from a fit of the fluorescence recovered intensity to Eq. (1) , and τ Diff is obtained from a fit to Eq. (2) (see text). FRAP measurements are performed with Coumarin 1 (1.3 × 10−3 M) in PPG 4000 M at T = 20 °C.
Fractional recovered fluorescence intensity, f, of Coumarin 1 (1.3 × 10−3 M) in PPG 4000 M as a function of t/τ Diff. Pressure is varied from 200 to 2500 bar at room temperature T = 20 °C.
Translational diffusive coefficient, D, of Coumarin 1 in PPG as a function of pressure P. Colour symbols: Present measurements in PPG 1000 M (blue diamonds) and PPG 4000 M (magenta triangles). Solid lines: Fit to Eq. (7) of the experimental data in the pressure range P < 1500 bar. Black circles: Diffusion coefficient D S−E in PPG 1000 M calculated from the Stokes-Einstein equation. Error bars are of the size of the symbols.
Normalized translational diffusive coefficient, D/D S−E , as a function of pressure P. At the crossover pressure P ≈ 1500 bar the translational diffusive coefficient D of Coumarin 1 in PPG becomes decoupled from D S−E . Dashed lines are a guide to the eye.
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