Solvation dynamics and rotational relaxation in supercritical fluids have been examined using the techniques of the subpicosecond laser spectroscopy. The fluorescence up-conversion technique has been employed to detect the fluorescence anisotropy decay of coumarin 153 in supercritical CO 2 (310 K) and CHF 3 (302, 310 K) over a wide density range. The rotational correlation times in supercritical CHF 3 exhibit the remarkable increase at 0.6 0.7 times ρ c, which implies that the local solvent density augmentation slows down the rotational dynamics in supercritical fluids. This conclusion is supported by computer simulations based on a 2-site model of fluoroform. The solvation dynamics of the probe 4-dimethylamino-4′-cyanostilbene have been measured in supercritical CHF 3 at 310 K using the optical Kerrgated emission technique, which appears to have captured most (∼90%) of the dynamics occurring over the accessible density range between 1.4-2.0ρ c. The measured spectral response exhibits a bimodal decay with ∼0.6 ps and ∼9 ps components and only a modest density dependence.
|Original language||English (US)|
|Number of pages||7|
|Journal||Review of High Pressure Science and Technology/Koatsuryoku No Kagaku To Gijutsu|
|State||Published - 2006|
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics