High-pressure studies of rotational reorientation dynamics: The role of dielectric friction

Journal Article · Sun Dec 01 04:00:00 EST 1985 · J. Chem. Phys.; (United States)

DOI:https://doi.org/10.1063/1.449661· OSTI ID:6487352

Philips, L A; Webb, S P; Clark, J H

Picosecond, time-resolved, fluorescence depolarization spectroscopy is used to measure the rotational reorientation times of rhodamine 6G (R6G) and p-terphenyl (PTP) as a function of solvent viscosity. The viscosity is varied either by changing the solvent or by changing the pressure in a single solvent. The differences between the two molecules, PTP and R6G, provide a means of evaluating the role of solute structure and solute--solvent interactions on the dynamics of rotational reorientation. The rotational behavior of PTP is well described by simple hydrodynamic models as embodied by the Stokes--Einstein--Debye equation. In contrast, the rotational reorientation dynamics of the charged molecule R6G are not well described by these models. It is demonstrated that dielectric friction plays an important role in governing the rotational motion of charged molecules in polar solvents. When the solvent dielectric properties are varied, the dielectric friction model accurately predicts the observed experimental trends under a wide variety of experimental conditions. This model is also shown to explain anomalous effects previously attributed to the presence of solute--solvent hydrogen bonded complexes.

• Research Organization: Laboratory of Chemical Biodynamics, Lawrence Berkeley Laboratory, and Department of Chemistry, University of California, Berkeley, California 94720
• OSTI ID: 6487352
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 83:11; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
AMINES
AROMATICS
CARBOXYLIC ACIDS
DIELECTRIC PROPERTIES
DYES
ELECTRICAL PROPERTIES
FLUID MECHANICS
FLUIDS
FLUORESCENCE
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HIGH PRESSURE
HYDROCARBONS
HYDRODYNAMICS
LIQUIDS
LUMINESCENCE
MECHANICS
MOTION
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
POLYPHENYLS
REAGENTS
RHODAMINES
ROTATION
TERPHENYL-PARA
TERPHENYLS
VISCOSITY