Negatively charged water clusters: mass spectra of (H2O)n- and (D2O)n-

Haberland, Hellmut; Langosch, H.; Schindler, Hansgeorg; Worsnop, D. R.

doi:10.1021/j150661a042

Cited by 150 publications

(115 citation statements)

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“…23 They observed water dimer anions, clusters comprising n ) 6 and 7 molecules, and a continuous cluster distribution from n ) 11 to 25. The first photoelectron spectra of water cluster anions were reported by Bowen 17 in the size range n ) 2-69.…”

Section: Water Cluster Anionsmentioning

confidence: 97%

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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Section: Water Cluster Anionsmentioning

confidence: 97%

Dynamics of Electron Solvation in Molecular Clusters

Ehrler

Neumark

2009

Acc. Chem. Res.

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“…116 The (H 2 O) n -mass spectrum is dominated by peaks at n = 2, 6, 7, and 11. 113,116,145 The origin of this intensity pattern is still under debate.…”

Section: General Considerationsmentioning

confidence: 99%

“…116 Figure 8 reproduces a mass spectrum of (H 2 O) n -clusters from the Johnson group. 113 This spectrum is noteworthy by the absence of a peak for the monomer, consistent with its dipole moment being too small to support a dipole-bound anion, and by the occurrence of magic numbers at n = 2, 6, 7, and 11, and a monotonically decreasing intensity distribution for n ¥ 15.…”

Section: General Considerationsmentioning

confidence: 99%

A Drude-model approach to dispersion interactions in dipole-bound anions

Wang¹,

Jordan²

2001

The Journal of Chemical Physics

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A one-electron model potential for calculating the binding energy of an excess electron interacting with polar molecules and their clusters is described. The unique feature of this potential is the treatment of polarization and dispersion effects by means of a Drude model. The approach is tested by calculating the energies for binding an excess electron to HCN, (HCN)2, HNC, and (HNC)2. The model potential results are found to be in good agreement with the predictions of high-level all-electron calculations.

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“…Water cluster anions are usually prepared in molecular jets after an expansion of water vapor. 19,20,73 The initially formed neutral water clusters collide with slow secondary electrons of an electron source, and bind the electrons. Although the exact mechanism of cluster formation and the following electron attachment is not known, simple models of the process can be invented and studied by molecular dynamics.…”

Section: Resultsmentioning

confidence: 99%

“…Mixed quantum-classical molecular dynamics (QCMD) simulations modeling solvent particles classically, while describing solutes quantum mechanically still offer a reasonable compromise between sophistication and effectiveness. 16,17,18 Negatively charged water clusters, also known as hydrated electron clusters, 19,20 can be viewed as one of the simplest conceivable solvent-solute systems, an ideal target for QCMD simulations. Within the QCMD framework, the quantum mechanical solute, the excess electron, having only electronic, but no nuclear degrees of freedom, is embedded in a classical bath of a handful of water molecules.…”

Section: Introductionmentioning

confidence: 99%

Hydration dynamics in water clusters via quantum molecular dynamics simulations

Túri

2014

The Journal of Chemical Physics

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We have investigated the hydration dynamics in size selected water clusters with n=66, 104, 200, 500 and 1000 water molecules using molecular dynamics simulations. To study the most fundamental aspects of relaxation phenomena in clusters, we choose one of the simplest, still realistic, quantum mechanically treated test solute, an excess electron. The project focuses on the time evolution of the clusters following two processes, electron attachment to neutral equilibrated water clusters and electron detachment from an equilibrated water cluster anion. The relaxation dynamics is significantly different in the two processes, most notably restoring the equilibrium final state is less effective after electron attachment. Nevertheless, in both scenarios only minor cluster size dependence is observed. Significantly different relaxation patterns characterize electron detachment for interior and surface state clusters, interior state clusters relaxing significantly faster. This observation may indicate a potential way to distinguish surface state and interior state water cluster anion isomers experimentally. A Cluster relaxation was also investigated using two different computational models, one preferring cavity type interior states for the excess electron in bulk water, while the other simulating non-cavity structure. While the cavity model predicts appearance of several different hydrated electron isomers in agreement with experiment, the non-cavity model locates only cluster anions with interior excess electron distribution. The present simulations show that surface isomers computed with the cavity predicting potential show similar dynamical behavior to the interior clusters of the non-cavity type model. Relaxation associated with cavity collapse presents, however, unique dynamical signatures.

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Negatively charged water clusters: mass spectra of (H2O)n- and (D2O)n-

Cited by 150 publications

References 1 publication

Dynamics of Electron Solvation in Molecular Clusters

Dynamics of Electron Solvation in Molecular Clusters

A Drude-model approach to dispersion interactions in dipole-bound anions

Hydration dynamics in water clusters via quantum molecular dynamics simulations

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