Resonance Raman Spectra of Electrons Solvated in Liquid Alcohols

Tauber, Michael J.; Stuart, Christina M.; Mathies, Richard A.

doi:10.1021/ja031816d

Cited by 30 publications

(58 citation statements)

References 42 publications

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“…These efforts are backed by extensive benchmark calculations (27,28) for both (H 2 O) n Ϫ and (HF) n Ϫ , indicating that electron correlation effects are weak in the case of an ''excess'' electron bound by one or more closed-shell molecules. As such, the simulation techniques described here are applicable to other solvated-electron systems of contemporary interest, including electrons solvated in ammonia (33), alcohols (34), and organic ionic liquids (35). In addition, simulations of weakly bound molecular anions may provide important information regarding the mechanisms underlying biological radiation damage, as recent calculations suggest that low-energy electron binding by * orbitals of DNA bases is one such damage pathway (36).…”

Section: Discussionmentioning

confidence: 99%

First-principles, quantum-mechanical simulations of electron solvation by a water cluster

Herbert

Head‐Gordon²

2006

Proc. Natl. Acad. Sci. U.S.A.

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Despite numerous experiments and static electronic structure calculations, the nature of hydrated-electron clusters, (H2O) n ؊ , remains poorly understood. Here, we introduce a hybrid ab initio molecular dynamics scheme, balancing accuracy against feasibility, to simulate vibrational and photoelectron spectra of (H2O) n ؊ , treating all electrons quantum-mechanically. This methodology provides a computational tool for understanding the spectra of weakly bound and supramolecular anions and for elucidating the fingerprint of dynamics in these spectra. Simulations of (H2O) 4 ؊ provide quantitative agreement with experimental spectra and furnish direct evidence of the nonequilibrium nature of the cluster ensemble that is probed experimentally. The simulations also provide an estimate of the cluster temperature (T Ϸ 150 -200 K) that is not available from experiment alone. The ''double acceptor'' electron-binding motif is found to be highly stable with respect to thermal fluctuations, even at T ‫؍‬ 300 K, whereas the extra electron stabilizes what would otherwise be unfavorable water configurations.ab initio molecular dynamics ͉ hydrated electron ͉ photoelectron spectroscopy T he hydrated electron (1), e aq Ϫ , is an important intermediate in the chemistry of aqueous systems exposed to ionizing radiation, including water droplets in the upper atmosphere, nuclear fission reactors, radioactive waste, and, upon irradiation, living tissue. Anionic water clusters undergo the same electronscavenging reactions as does the aqueous electron (2) and provide a means for studying stepwise evolution toward e aq Ϫ . Vertical electron-binding energies (VEBEs) have been measured, by photoelectron spectroscopy, for all (H 2 O) n Ϫ clusters with n ϭ 2-11 and many larger clusters (3-6). As n increases, the dominant feature in these spectra shifts to higher energy, but this otherwise smooth evolution is interrupted at n ϭ 4 by an abrupt jump to much higher energy, which has been interpreted as the onset of a common structural motif among the n ϭ 4-11 clusters (5). Here, we study (H 2 O) 4 Ϫ as a representative example (7-9) of this electron-binding motif.Vibrational spectra (7-10) for small hydrated-electron clusters (n Յ 6) reveal an electron-binding motif thought to be inconsistent with the spectral signatures of e Ϫ in bulk water (11,12), suggesting that the manner in which water networks bind an extra electron changes qualitatively as a function of cluster size. Vibrational (7-10, 13, 14), electronic (15-18), and photoelectron (3-6) spectra of size-selected (H 2 O) n Ϫ clusters have been measured across a wide range of n but are difficult to interpret in the absence of detailed calculations. For n Ͼ 6, the vibrational spectra have not yet been assigned to particular isomers and probably include contributions from multiple isomers, because these clusters are likely to possess significant internal energy (19,20). An estimate of this internal energy is essential to interpreting the spectra, because clusters are prone to exhibit multiple...

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Section: Discussionmentioning

confidence: 99%

First-principles, quantum-mechanical simulations of electron solvation by a water cluster

Herbert

Head‐Gordon²

2006

Proc. Natl. Acad. Sci. U.S.A.

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“…This would provide for a continuous evolution to the structure of the solvated electron in liquid methanol whose suggested structure is for the OH groups of the alcohol to be directed toward the electron's center of mass. 19,22,70 Time-resolved experiments 25 on photodetachment of I − in bulk methanol and related theoretical treatments 71,72 indicate that CTTS excitation leads to formation of an I:e − "contact pair" on a time-scale of 200-300 fs. The newly formed electron can undergo either diffusive escape to form a solvated electron or geminate recombination with the iodine atom.…”

Section: Comparison To Larger Systemsmentioning

confidence: 99%

“…Its similarities and differences compared to water allow for a better understanding of how the local solvent environment affects electron solvation and solvent relaxation. To this end, numerous experimental [15][16][17][18][19][20][21] and theoretical [22][23][24] investigations have been carried out on the dynamics of electron solvation in methanol. For example, ultrafast transient absorption experiments have been utilized by Bradforth and co-workers 5,25 to probe the CTTS dynamics from iodide in water, methanol, and lower alcohols.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of electron solvation in I−(CH3OH)n clusters (4 ≤ n ≤ 11)

Young

Yandell

Neumark

2011

The Journal of Chemical Physics

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The dynamics of electron solvation following excitation of the charge-transfer-to-solvent precursor state in iodide-doped methanol clusters, I(-)(CH(3)OH)(n = 4-11), are studied with time-resolved photoelectron imaging. This excitation produces a I···(CH(3)OH)(n)(-) cluster that is unstable with respect to electron autodetachment and whose autodetachment lifetime increases monotonically from ~800 fs to 85 ps as n increases from 4 to 11. The vertical detachment energy (VDE) and width of the excited state feature in the photoelectron spectrum show complex time dependence during the lifetime of this state. The VDE decreases over the first 100-400 fs, then rises exponentially to a maximum with a ~1 ps time constant, and finally decreases by as much as 180 meV with timescales of 3-20 ps. The early dynamics are associated with electron transfer from the iodide to the methanol cluster, while the longer-time changes in VDE are attributed to solvent reordering, possibly in conjunction with ejection of neutral iodine from the cluster. Changes in the observed width of the spectrum largely follow those of the VDEs; the dynamics of both are attributed to the major rearrangement of the solvent cluster during relaxation. The relaxation dynamics are interpreted as a reorientation of at least one methanol molecule and the disruption and formation of the solvent network in order to accommodate the excess charge.

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“…Consequently, many studies have been performed on the hydrated electron [6][7][8][9][10][11] and its cluster counterparts, [12][13][14][15][16][17][18] ͑water͒ n − . The solvated electron in liquid methanol has also received considerable experimental [19][20][21][22] and theoretical [23][24][25] attention. However, only very few studies have been made of ͑methanol͒ n − clusters, [26][27][28] and here, we present the first studies of timeresolved dynamics in these species.…”

Section: Introductionmentioning

confidence: 99%

Time-resolved photoelectron imaging of large anionic methanol clusters: (Methanol)n−(n∼145–535)

Kammrath

Griffin

Verlet

et al. 2007

The Journal of Chemical Physics

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The dynamics of an excess electron in size-selected methanol clusters is studied via pump-probe spectroscopy with resolution of approximately 120 fs. Following excitation, the excess electron undergoes internal conversion back to the ground state with lifetimes of 260-175 fs in (CH3OH)n- (n=145-535) and 280-230 fs in (CD3OD)n- (n=210-390), decreasing with increasing cluster size. The clusters then undergo vibrational relaxation on the ground state on a time scale of 760+/-250 fs. The excited state lifetimes for (CH3OH)n- clusters extrapolate to a value of 157+/-25 fs in the limit of infinite cluster size.

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Resonance Raman Spectra of Electrons Solvated in Liquid Alcohols

Cited by 30 publications

References 42 publications

First-principles, quantum-mechanical simulations of electron solvation by a water cluster

First-principles, quantum-mechanical simulations of electron solvation by a water cluster

Dynamics of electron solvation in I−(CH3OH)n clusters (4 ≤ n ≤ 11)

Time-resolved photoelectron imaging of large anionic methanol clusters: (Methanol)n−(n∼145–535)

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