Optical Absorption of Solvated Electrons in Water and Tetrahydrofuran/Water Mixtures

Abstract

In the past Jou and Dorfman (J. Chem. Phys. 1973, 58, 4715) have determined the optical absorption spectra of solvated electrons (esolv -) in binary mixtures of tetrahydrofuran (THF) and water over the entire concentration range. From these experiments they concluded that the position of the absorption maximum and the width at half-height of the band are dominated by water. By additional experiments we show that at least for some mixtures with a mole fraction X(THF) ≤ 0.50, we obtain spectra at 298 K which agree almost completely with those of esolv - in pure water at elevated temperatures obtained by Jou and Freeman (J. Phys. Chem. 1979, 83, 2383). It follows that for this range of composition, excess electrons are obviously hydrated and the large amount of THF of up to X(THF) = 0.49 changes the water structure of the hydrated electron only slightly. The same effect can be produced by a temperature increase of T = 80 K in pure water. From the spectra we have determined equilibrium ground-state properties of the hydrated electron as a function of temperature and composition of the mixture. Results of quantum-statistical simulations on hydrated electrons show very poor agreement with the experimental results. Therefore, it seems to be presumptuous to take these simulations as a basis to explain the behavior of excess electrons in water on a femtosecond time scale.

Is there any Correlation between the Mobility and the Absorption Spectra of Solvated Electrons in Polar Solvents?

“…Hertwig, Hippler and Unterreiner [24] demonstrated that the spectrum of the relaxing hydrated electron is blue-shifted during this process with a time constant τ ϭ 300Ϯ50 fs. The assumptions for the simple evaluation of the experimental observations are: The oscillator strength is 1 and the spectra show shape stability [9,25,26]. This observation sustains our former suggestion [22].…”

“…However, up to now it is difficult to calculate the optical spectra with these methods (for a critical comparison between theory and experiment see [9]). Therefore, it is suggested that there are Brought to you by | The University of Auckland Library Authenticated Download Date | 6/22/15 3:30 AM similar problems with the simulation of correlation functions like the displacement correlation function (Eq.…”

“…It was shown in the past that the low frequency side of the e Ϫ solv absorption spectrum can be approximately fitted by a Gaussian line shape function with the partial halfwidth W low measured from ប ω max to the energy at half-height on the red side of the spectrum [8,9] σ(ω) ϭ σ(ω max ) exp{Ϫ[(បω Ϫ បω max )/W low ] 2 ln 2} for ω Յ ω max . (8) If there would be in fact a contribution of the optical absorption to the electron mobility depending on ប ω max one has to assume for the sake of argument that the Gaussian line shape is valid for the frequency range 0 Յ ω Յ ω max .…”

Degradation of an Ethylene Carbonate/Diethyl Carbonate Mixture by Using Ionizing Radiation

“…[22,23] In this case, and for am olar fraction of THF lower than 0.49, the presence of THF only slightly changed the spectrum of the solvated electron, which was similar to the spectrum of the solvated electron in water,b ut at ah igher temperature. [23] In our case, the transients pectrum we measured (for am olar fraction of DEC equal to 0.43) is similart ot hat obtained in EC, butr edshifted ( Figure 2). In contrast with the measurements performed for THF/water mixtures, forw hich the time-resolveds pectra exhibited isosbestic points andt he hydration dynamicsw as describedb yt wo-state kinetics, which implied thatn anometer inhomogeneities exist in these mixtures, no such trend was observed here (Figure 1c), which suggests that the EC/DEC mixture is homogeneous even at the [24] The band of the solvated electron in EC/ DEC is broader than that measured in neat EC, as clearly shown by the spectrum measured2 0psa fter the electron pulse ( Figure 2).…”

Temperature Effect on the Absorption Spectrum of the Hydrated Electron Paired with a Lithium Cation in Deuterated Water

“…We note that the spectral broadening in the presence of high-concentration metallic salt is still an arguable subject. 39,45,56 Bonin et al 45 and Marbach et al 56 claimed the spectral stability of the absorption spectrum of solvated electrons observed in concentrated salt solutions in water or in mixtures of THF/water by laser photolysis experiments, while Kreitus 39 reported a spectral broadening with increasing LiCl concentration by pulse radiolysis measurements.…”