ENERGETICS AND DISPERSION OF OPTICAL ELECTRON TRANSFER IN SOLUTION (SOLVATION, POLARIZABILITY)

The energetics of photoelectron emission are discussed on the basis of thermodynamic considerations and a treatment of nuclear relaxation subsequent to optical electron transfer. A theory is developed for the calculation of the free energy of inner-sphere reorganization of univalent anions from their free energies of hydration. Calculated free energies of emission are in good agreement with experimental threshold energies for metal hexaquo cations and complexes and inorganic anions. Gas- and liquid-phase ionization energies are also correlated in agreement with experimental results for inorganic anions.;The effect of dielectric dispersion of the solvent on the energetics of optical electron transfer is determined quantitatively by variations of the free energy of solvation of the species being photoionized. The solvation free energy varies because the solvent polarizability in the inner-sphere region of the photon absorbing species changes with photon energy on account of dispersion. The solvation free energy is computed for a varying polarizability of the solvent in the inner-sphere region with fixed nuclear configuration of the solvent. The change in solvation free energy in aqueous solution is computed in the 7 to 11 eV range from data on the refractive index of water obtained by reflectance spectroscopy. The theory accounts quantitatively for the effect of dispersion on photoelectron emission by aqueous solutions of anions, cations and molecules.;Improvements in the instrumentation and methodology of photoelectron emission spectroscopy of solutions are discussed. The application of digital filters in this work is surveyed.;Thermal and optical electron transfer processes in solution are correlated. Activation free energies for electron exchange in solution are calculated from experimental reorganization free energies for emission in excellent agreement with experimental kinetic data for metal hexaquo cations and complexes. The correlation between charge transfer spectra of anions and the corresponding threshold energies for emission is applied to the calculation of the reorganization free energy of the hydrated electron. Kinetic implications are discussed.