Dispersion spectroscopy of optical electron transfer in solution

Abstract

The effect of dielectric dispersion of the solvent on optical electron transfer is interpreted as a shift ΔGd of the free energy level of the ground state in the photoionization process. The shift ΔGd is derived for transparent and absorbing solvents by application of the Marcus theory of nonequilibrium polarization of a continuous medium. Only the inner-sphere solvation shell contributes significantly to the dispersion correction ΔGd. Application is made to photoelectric emission by solutions. The effect of dispersion on the energetics of emission causes deviation from the expected emission law. The resulting dispersion spectra are obtained for photoelectron emission by 17 inorganic anions in aqueous solution in the 7 to 10 eV range of photon energies. The spectra primarily result from dispersion of the solvent and are not strongly affected by the nature of the photoionized anion. Experimental dispersion spectra agree well with the theoretical spectrum predicted from the real and imaginary dielectric constants obtained from reflectance spectroscopy data of liquid water. Dispersion spectroscopy of optical electron transfer developed in this work provides an experimental probe of the inner-sphere solvation shell.

Using cluster studies to approach the electronic structure of bulk water: Reassessing the vacuum level, conduction band edge, and band gap of water

“…͑2͒ and knowledge of ⌬E sol (A), ⌬E sol (A), and AEA͓A(g)͔. These quantities, [12][13][14] PETs, [15][16][17][18][19] and VDEs 9-11 can be found in Table I for the e Ϫ , I Ϫ , Br Ϫ , Cl Ϫ , and OH Ϫ defects. The radical solvation energies, ⌬E sol (A), are the least well-known of these quantities, but they are also much smaller than the other terms.…”

“…5, it is evident that the band gap of water can not be determined with a vertical transition; hence no experiment has succeeded in directly measuring this property. On this diagram, the four upwardly directed arrows from the edge of their state levels represent vertical, experimentally observed thresholds, including the photoemission threshold from pure water 15 (PET͓H 2 O(l)͔ϭ10.06 eV), the photoemission threshold [16][17][18][19] from hydroxide in water (PET͓OH Ϫ (aq)͔ ϭ8.45 eV), the photoconductivity threshold 70 of hydrated electrons in ice (PCT͓e Ϫ (ice)͔ϭ2.3 eV), and the photoemission threshold of hydrated electrons in water (PET͓e Ϫ (aq)͔ϷPCT͓e Ϫ (ice)͔ϪV 0 ϭ2.4 eV). None of these PETs accesses the conduction band at the vacuum level which has been placed ϳ0.1 eV above the conduction band edge by our preferred value 59 of ϳϪ0.1 eV for V 0 .…”

Ionization energies of liquids from energy distribution, quantum yield and second derivative curves

“…Such a functional dependence of the yield Y on photon energy is not rigorous. Moreover, the threshold energy Et varies with the photon energy E at which Y is measured because of the dielectric dispersion of the liquid [7,15]. Variations of Y1In with E therefore are modulated by the dispersion effect.…”

“…Quantum yield spectra were determined with the equipment used in earlier work [6] after numerous improvements [7]. The instrument resolution was better than 0.1 eV at 10 eV and lower photon energies.…”

Transition dipole-solvent interaction in photoionization

“…This was shown in ref. [3] for aqueous solutions of 17 inorganic anions with threshold energies ranging from 7.2 to 8.9 eV.…”