Band resolution of optical spectra of solvated electrons in water, alcohols, and tetrahydrofuran

Abstract

The optical absorption spectra of solvated electrons in water, alcohols, and tetrahydrofuran are empirically resolved into two Gaussian bands and a continuun~ tail. The first Gaussian band covers most of the low energy side of the spectrum. The second Gaussian band lies at an energy slightly above that of the absorption maximum of the total spectrum. With the exception of teit-butyl alcohol, in water and alcohols the following were obserbed: ( 0 ) the first Gaussian bands have the same half-width, but the oscillator strength in water is about double that in an alcohol; (b) the second Gaussian bands have similar half-widths and oscillator strengths; (c) the continuum tails have similar half-midths, yet that in water possesses only about one third as much oscillator strength as one in an alcohol. 711 tert-butyl alcohol and tetrahydrofuran the first Gaussian band and the continuum tail each carry nearly half of the total oscillator strength. Chem. 57.591 (1979) Les spectres d'absorbtion optique des electrons solvates dams l ' e a~~, les alcools et le tetrahydrofuranne peuvent @tre resolus en~piriquement en deux courbes gaussiennes et en Line queue continue. La premiere courbe gaussienne recouvre presque toute la partie de faible energie du spectre. La deuxien~e courbe gaussienne se trouve a une energie Iegerement superieure au maxiillurn d'absorbtion du spectre global. A I'exception du teii-butanol, on observe generalement avec I'eau et les alcools, les faits suivants: (cr) les largeurs a demi-hauteur des premieres courbes gaussiennes sont approximativernent les rnsmes; la force de I'oscillateur dans I'eau est approximativement deux fois celle dans l'alcool: ( b ) les largeurs a demi-hauteur et les forces des oscillateurs des deuxiemes courbes gaussiennes sont semblables; (c) les largeurs a demi-qauteur des queues continues sont semblables; toutefois la force de l'oscillateur de celle de I'eau est environ trois fois rnoindre que celle d'un alcool. Dans le reri-butanol el le tetrahydrofuranne la force de I'oscillateur de la premiere courbe gaussienne est approximativement igal a cela de la queue continue. FANG-YVAN[Traduit par le journal] Introduction the \.lings OF the spectrum. Therefore. we have

Analysis of localization sites for an excess electron in neutral methanol clusters using approximate pseudopotential quantum-mechanical calculations

“…14,15,16 This approach has provided a molecular level picture of the bulk solvated electron in methanol 17,18,19,20,21,22,23 that is consistent with experimental observations. 24,25,26,27,28,29,30 Despite the general qualitative agreement of experiment and theory, it was found that the measured position and the halfwidth of the optical spectrum of the solvated electron in methanol 26 is not satisfactorily predicted in simulations. 18 To remedy this inadequacy, a new electron-methanol molecule pseudopotential has been developed recently using static exchange pseudopotential theory.…”

Quantum-classical simulation of electron localization in negatively charged methanol clusters

“…1,2,3,4,5,6,7,8,9,10 The similarities and the differences of methanol as a solvent compared to water provide the main motivation for the scientific interest in studying electron solvation in methanol. A more complete understanding of electron solvation can be reached not only by varying the polar solvent but also by extending the investigations from bulk solvents to finite size solvated electron systems, negatively charged solvent clusters.…”

“…28 These simulations notably improved the position and the half-width of the optical spectrum of the solvated electron in bulk methanol in comparison with experiments. 3 This is important since, for the clusters experimentally assigned as having interior-bound electrons a strong detachment feature of the two-photon photoelectron spectrum using 1.55 eV excitation indicated the presence of a well-defined excited state that was accessible at 1.55 eV. 9 This would be consistent with the existence of a cluster-supported excited state similar to the broad absorption evident for the bulk solvated electron in methanol, peaked experimentally at 1.9 eV.…”

A new electron-methanol molecule pseudopotential and its application for the solvated electron in methanol

“…2,3,4,5,6,7,8 Methanol, similarly to other polar solvents, localizes the excess electron in a solvent cavity surrounded by properly oriented methanol molecules. According to the ESR measurements of Kevan et al on excess electrons in low-temperature methanol glass, the first solvation shell contains 4±2 methanol molecules with an average hydroxyl hydrogen -electron distance of 2.3±0.15 Å.…”

“…3 The steadystate absorption spectrum of the solvated electron in methanol exhibits a broad, asymmetric band with a maximum at 1.95 eV. 4 The advance of ultrafast laser techniques made it also possible to investigate the relaxation dynamics of the excess electrons in methanol on the subpicosecond timescale. 5,6 More recently, resonance Raman experiments of Mathies et al…”