Picosecond studies of structure and dynamics of electronically excited molecules in solution. [Rotational reorientation times]

Technical Report · Mon Apr 01 04:00:00 EST 1985

OSTI ID:5561574

Philips, L A

Picosecond spectroscopy was used to probe the liquid phase dynamics of two different chemical systems. In the first study, the rotational reorientation times of rhodamine 6G (R6G) and p-terphenyl (PTP) were measured as a function of solvent viscosity. The viscosity was varied either by changing the solvent or by changing the pressure in a single solvent. The differences between the two molecules PTP and R6G provided a means of evaluating the role of solute structure and solute-solvent interactions on the dynamics on rotational reorientation. For example, the rotational behavior of PTP was well described by simple hydrodynamic models as embodied in the Stokes-Einstein-Debye equation. In contrast, the rotational reorientation dynamics of the charged molecule R6G were not well described by these models. High pressure techniques were developed for this study to provide a means of varying the viscosity of a single solvent. The new information from these experiments demonstrated that dielectric friction plays an important role in governing the rotational motion of charged solute molecules in polar solvents. The second study employed both time resolved emission and time resolved resonance Raman spectroscopies to examine the ultrafast photophysics of ruthenium tris-2,2' bipyridine in aqueous solution. The structural specificity of Raman spectroscopy enabled the identification of the electronically excited species. It was determined that in the excited state, the electron undergoing the metal-to-ligand-charge-transfer (MLCT) is localized on a single bipyridine ligand with 25 ps of excitation. Additional information from the time resolved emission studies provided insight into the rate of relaxation through the manifold of excited electronic states. 155 refs., 48 figs., 37 tabs.

• Research Organization: Lawrence Berkeley Lab., CA (USA)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 5561574
• Report Number(s): LBL-19511; ON: DE85015115
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
400301* -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
AMINES
AQUEOUS SOLUTIONS
AROMATICS
AZINES
BIPYRIDINES
CARBOXYLIC ACIDS
COMPLEXES
DATA
DISPERSIONS
DYES
ENERGY LEVELS
EXCITED STATES
EXPERIMENTAL DATA
FLUIDS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HYDROCARBONS
HYDROGEN COMPOUNDS
INFORMATION
LIQUIDS
MIXTURES
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
ORGANIC SOLVENTS
OXYGEN COMPOUNDS
POLYPHENYLS
PYRIDINES
RAMAN SPECTRA
REAGENTS
RHODAMINES
ROTATIONAL STATES
RUTHENIUM COMPLEXES
SOLUTIONS
SOLVENTS
SPECTRA
SPECTROSCOPY
TERPHENYL-PARA
TERPHENYLS
TRANSITION ELEMENT COMPLEXES
VERY HIGH PRESSURE
VISCOSITY
WATER