Structure of the hydrated electron

Hameka, Hendrik F.; Robinson, G. W.; Marsden, Colin J.

doi:10.1021/j100296a010

Cited by 76 publications

(55 citation statements)

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“…One cannot resist commenting that this configuration is, in fact, an incipient form of the OH − ·H 3 O description of the hydrated electron put forward by Hameka et al 59 and more recently considered by Sobolewski and Domcke. I that the donor ͑H2͒ hydrogen supporting the AA molecule plays an increasingly important role in the normal mode ͑Q s ͒, nominally assigned to the symmetric stretch, as the cluster size increases from n = 4-6.…”

Section: E Implications Of the Aa Binding Motif: Vibronic Interactiomentioning

confidence: 91%

Vibrational predissociation spectroscopy of the (H2O)6–21− clusters in the OH stretching region: Evolution of the excess electron-binding signature into the intermediate cluster size regime

Hammer

Roscioli

Bopp

et al. 2005

The Journal of Chemical Physics

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We report vibrational predissociation spectra of the (H2O)n- cluster ions in the OH stretching region to determine whether the spectral signature of the electron-binding motif identified in the smaller clusters [Hammer et al. Science 306, 675 (2004)] continues to be important in the intermediate size regime (n = 7-21). This signature consists of a redshifted doublet that dominates the OH stretching region, and has been traced primarily to the excitation of a single water molecule residing in a double H-bond acceptor (AA) binding site, oriented with both of its H atoms pointing toward the excess electron cloud. Strong absorption near the characteristic AA doublet is found to persist in the spectra of the larger clusters, but the pattern evolves into a broadened triplet around n = 11. A single free OH feature associated with dangling hydrogen atoms on the cluster surface is observed to emerge for n > or = 15, in sharp contrast to the multiplet pattern of unbonded OH stretches displayed by the H+(H2O)n clusters throughout the n = 2-29 range. We also explore the vibration-electronic coupling associated with normal-mode displacements of the AA molecule that most strongly interact with the excess electron. Specifically, electronic structure calculations on the hexamer anion indicate that displacement along the -OH2 symmetric stretching mode dramatically distorts the excess electron cloud, thus accounting for the anomalously large oscillator strength of the AA water stretching vibrations. We also discuss these vibronic interactions in the context of a possible relaxation mechanism for the excited electronic states involving the excess electron.

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Section: E Implications Of the Aa Binding Motif: Vibronic Interactiomentioning

confidence: 91%

Vibrational predissociation spectroscopy of the (H2O)6–21− clusters in the OH stretching region: Evolution of the excess electron-binding signature into the intermediate cluster size regime

Hammer

Roscioli

Bopp

et al. 2005

The Journal of Chemical Physics

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“…19 Other alternative models attribute the characteristic hydrated electron properties (in particular, its absorption spectrum, see below) to molecular species other than water molecules. Such species include the hydrated hydronium molecule-hydroxide ion pair (H 3 O…OH -), 182 the solvated solvent-anion complex, 183 and the hydrated hydronium radical. 184,185,186 In the following, we overview the experimental observations directly related to the structural aspects of the hydrated electron and confront them with the predictions of various theoretical approaches.…”

Section: Structural Models and Energetics Of The Hydrated Electronmentioning

confidence: 99%

Theoretical Studies of Spectroscopy and Dynamics of Hydrated Electrons

2012

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“…7 An alternate picture, the so-called chemical model, has also been proposed suggesting that the electron resides in a diffuse orbital on a neutral H 3 O radical. 8 Formation of e aq -in the bulk generally proceeds either by ionization of the solvent or by detachment from a solute. 9 Both processes can produce highly excited electrons that relax through a combination of solvent dynamics and nonadiabatic transitions, and unraveling the overall relaxation mechanism has proved challenging.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of Electron Solvation in Molecular Clusters

Ehrler

Neumark

2009

Acc. Chem. Res.

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S olvated electrons, and hydrated electrons in particular, are important species in condensed phase chemistry, physics, and biology. Many studies have examined the formation mechanism, reactivity, spectroscopy, and dynamics of electrons in aqueous solution and other solvents, leading to a fundamental understanding of the electron-solvent interaction. However, key aspects of solvated electrons remain controversial, and the interaction between hydrated electrons and water is of central interest. For example, although researchers generally accept that hydrated electrons, e aq -, occupy solvent cavities, another picture suggests that the electron resides in a diffuse orbital localized on a H 3 O radical. In addition, researchers have proposed two physically distinct models for the relaxation mechanism when the electron is excited. These models, formulated to interpret condensed phase experiments, have markedly different time scales for the internal conversion from the excited p state to the ground s state.Studies of negatively charged clusters, such as (H 2 O) n -and I -(H 2 O) n , offer a complementary perspective for studying aqueous electron solvation. In this Account, we use time-resolved photoelectron spectroscopy (TRPES), a femtosecond pump-probe technique in which mass-selected anions are electronically excited and then photodetached at a series of delay times, to focus on time-resolved dynamics in these and similar species. In (H 2 O) n -, TRPES gives evidence for ultrafast internal conversion in clusters up to n ) 100. Extrapolation of these results yields a p-state lifetime of 50 fs in the bulk limit. This is in good agreement with the nonadiabatic solvation model, one of the models proposed for relaxation of e aq -. Similarly, experiments on (MeOH) n -up to n ) 450 give an extrapolated p-state lifetime of 150 fs.TRPES investigations of I -(H 2 O) n and I -(CH 3 CN) n probe a different aspect of electron solvation dynamics. In these experiments, an ultraviolet pump pulse excites the cluster analog of the charge-transfer-to-solvent (CTTS) band, ejecting an electron from the iodide into the solvent network. The probe pulse then monitors the solvent response to this excess electron, specifically its stabilization via solvent rearrangement. In I -(H 2 O) n , the iodide sits outside the solvent network, as does the excess electron initially formed by CTTS excitation. However, the iodide in I -(CH 3 CN) n is internally solvated, and both experimental and theoretical evidence indicate that electrons in (CH 3 CN) n -are internally solvated. Hence, these experiments reflect the complex dynamics that ensue when the electron is photodetached within a highly confined solvent cavity.

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Structure of the hydrated electron

Cited by 76 publications

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Vibrational predissociation spectroscopy of the (H2O)6–21− clusters in the OH stretching region: Evolution of the excess electron-binding signature into the intermediate cluster size regime

Vibrational predissociation spectroscopy of the (H2O)6–21− clusters in the OH stretching region: Evolution of the excess electron-binding signature into the intermediate cluster size regime

Theoretical Studies of Spectroscopy and Dynamics of Hydrated Electrons

Dynamics of Electron Solvation in Molecular Clusters

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