Dielectric relaxation time, potential energy

At high viscosities or low temperatures, dielectric relaxation time xj may be larger than the mean radiative lifetime t/ of the molecule. This may decrease the O—O separation between absorption and emission. On the other hand, at high temperatures solvent relaxation may be promoted thermally decreasing xd and O—O separation may again decrease. A maximum value for Av (O—O) is expected at some intermediate temperatures. Besides the relaxation effects, the O—O separation can also be affected by environmental modification of the potential energy surfaces. 

Chief among the interfacial properties of aqueous systems that suggest the occurrence of thermal anomalies are the following index of refraction, density, activation energy for ionic conductance, rates of surface reactions, surface tension, surface potentials, membrane potentials, heats of immersion, zeta potentials, rate of nucleation, viscous flow, ion activities, proton spin lattice relaxation times, optical rotation, ultrasonic velocity and absorption, sedimentation rates, coagulation rates, and dielectric properties. 

AG(s) given in Equation 13.3 represents the situation after some time when the solvent has had time to relax around the new charges. It is of great interest to study also the situation immediately after excitation. The problem is that there are no reduction potentials for that situation. We first derive the relationship between E (D) and 1(D) with the help of the Bom equation. The ionization energy I is the oxidation potential in a medium with dielectric constant c = 1, while E is the same oxidation potential in a medium with the dielectric constant c after a sufficiently long time for the solvent to polarize (Hgure 13.4). We have (a is a solvent radius around the charge)... 

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