solvent Dependence of the Optical Absorption Spectrum of the solvated Electron

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Abstract
With the recent application of fast infra‐red detection to pulse radiolysis studies of the solvated electron, the optical absorption spectrum has now been observed into the wavelength region beyond 2000 mμ. It has thus been possible to determine the spectrum in such weakly‐polar liquids as tetrahydrofuran, diethylamine and others, and in binary solvent systems of tetrahydrofuran with other liquids.Data now available for a variety of liquids cover an enormous range with the maximum of the absorption band at 580 mμ to 2100 mμ. In the following weakly‐polar liquids the band maxima are: tetrahydrofuran 2100 ± 50, diethylamine 1900 ± 80, dimethoxyethane 1900 ± 150 and diethyl ether 2050 ± 150mμ.It has been shown for such liquids as ammonia and ethylenediamine that results from pulse radiolysis of the pure liquid and from alkalimetal solutions lead to the same absorption band for the solvated electron. In all binary solvent systems studied, only a single absorption band is seen with λmax intermediate to the maxima observed for the pure components. Most of the data suggest that selective solvation in microscopic domains of the individual component does not occur, and the observations do not seem to support those models which propose that the optical properties are determined only by solvation with a small number of molecules. In tetrahydrofuran‐water solutions, however, the water is dominant in determining the optical properties, whereas the tetrahydrofuran is dominant in determining the dielectric properties.There thus appears to be some selective interaction with the water.The data now available for various liquids suggest that the spectral position of λmax is determined by the structural class of the molecule as well as by the dielectric properties of the liquid.

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