Electron Photodetachment in Solution

Kloepfer, J. A.; Vilchiz, Victor H.; Lenchenkov, Victor; Bradforth, Stephen E.

doi:10.1021/bk-2002-0820.ch008

Cited by 32 publications

(101 citation statements)

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“…Previously, such yields had been estimated for two halide anions only, I -and Br -, and were found to be unity across their lower energy CTTS subband. 4,12 In this work, we present a larger pattern of these QYs. Our results suggest that polyatomic anions generally have QYs substantially lower than unity.…”

Section: Introductionmentioning

confidence: 94%

“…5(b). Following the approach used for iodide 4,6 and hydroxide, 10 we assumed that the lowest-energy (242 nm) kinetics correspond to the case when υ >> 1 and then optimized parameter υ ; this procedure gave υ ≈3 for 225 nm photoexcitation …”

Section: Simulation Of Kinetic Traces For Monovalent Anionsmentioning

confidence: 99%

“…For halide anions, the electron distribution changes from a narrow one to a broad one when the photon energy exceeds a certain threshold value. 4,6 The QY data suggest a systematic broadening of the electron distribution with the excitation energy (e.g., for SO 3 2-, CSN -, HS -, and I -) that accounts for the increase in the survival probability and the free electron yield. For iodide in water and sodide in THF, this increase has already been reported.…”

Section: Synopsismentioning

confidence: 99%

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Electron Photodetachment from Aqueous Anions. 3. Dynamics of Geminate Pairs Derived from Photoexcitation of Mono- vs Polyatomic Anions

Lian

Oulianov²,

Crowell³

et al. 2006

J. Phys. Chem. A

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Photostimulated electron detachment from aqueous inorganic anions is the simplest example of solvent-mediated electron transfer. As such, this photoreaction became the subject of many ultrafast studies. Most of these studied focussed on the behavior of halide anions, in particular, iodide, that is readily accessible in the UV. In this study, we contrast the behavior of these halide anions with that of small polyatomic anions, such as pseudohalide anions (e.g., HS -) and common polyvalent anions (e.g., kinetics. These analyses suggest that for polyatomic anions (including all polyvalent anions studied) the initial electron distribution has a broad component, even at relatively low photoexcitation energy. There seem to be no well-defined threshold energy below which the broadening of the distribution does not occur, as is the case for halide anions.Direct ionization to the conduction band of water is the most likely photoprocess broadening the electron distribution. The constancy of (near-unity) prompt quantum yields vs. the excitation energy as the latter is scanned across the lowest charge-transferto-solvent band of the anion is observed for halide anions and Fe(CN) 6 4-but not for other anions: the prompt quantum yields are considerably less than unity and depend strongly on the excitation energy. Our study suggests that halide anions are in the class of their own; photodetachment from polyatomic, especially polyvalent, anions follows a different set of rules.

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Section: Introductionmentioning

confidence: 94%

Section: Simulation Of Kinetic Traces For Monovalent Anionsmentioning

confidence: 99%

Section: Synopsismentioning

confidence: 99%

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Electron Photodetachment from Aqueous Anions. 3. Dynamics of Geminate Pairs Derived from Photoexcitation of Mono- vs Polyatomic Anions

Lian

Oulianov²,

Crowell³

et al. 2006

J. Phys. Chem. A

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“…Thus, any spectroscopic dynamics associated with CTTS electron ejection from atomic ions must directly reflect the motions of solvent molecules. To this end, the CTTS behavior of solvated I -, including its steady-state spectroscopy in various solution environments, [37][38][39][40][41][42][43][44][45][46] photoinduced electron yields, 3,[47][48][49][50][51][52] and ultrafast electron-transfer dynamics, [1][2][3][4][5]8,9,28 has been characterized extensively over the last 75 years. Figure 1a shows the CTTS absorption spectrum of aqueous I -(blue solid curve), which consists of two broad and featureless bands that peak at 225 and 193 nm; these bands are associated with the two spinorbit states ( 2 P 3/2 and 2 P 1/2 ) of the neutral I atom photoproduct.…”

Section: Introductionmentioning

confidence: 99%

“…Figure 1a shows the CTTS absorption spectrum of aqueous I -(blue solid curve), which consists of two broad and featureless bands that peak at 225 and 193 nm; these bands are associated with the two spinorbit states ( 2 P 3/2 and 2 P 1/2 ) of the neutral I atom photoproduct. 41 The dynamics following one-photon CTTS excitation of I -in polar liquids has been investigated extensively by Bradforth and co-workers [1][2][3][4][5]7,8 (as well as by others 9,28 ). A small subset of Bradforth and co-workers' ultrafast spectral measurements associated with the CTTS excitation of aqueous I -are highlighted in Figure 1b; 53 excitation of the I -CTTS band leads to the rapid (<100 fs) appearance of hydrated electrons with a near-unit quantum yield.…”

Section: Introductionmentioning

confidence: 99%

Ultrafast Charge-Transfer-to-Solvent Dynamics of Iodide in Tetrahydrofuran. 2. Photoinduced Electron Transfer to Counterions in Solution

Bragg

Schwartz

2008

J. Phys. Chem. A

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Although they represent the simplest possible charge-transfer reactions, the charge-transfer-to-solvent (CTTS) dynamics of atomic anions exhibit considerable complexity. For example, the CTTS dynamics of iodide in water are very different from those of sodide (Na -) in tetrahydrofuran (THF), leading to the question of the relative importance of the solvent and solute electronic structures in controlling charge-transfer dynamics. In this work, we address this issue by investigating the CTTS spectroscopy and dynamics of I -in THF, allowing us to make detailed comparisons to the previously studied I -/H 2 O and Na -/THF CTTS systems. Since THF is weakly polar, ion pairing with the counterion can have a substantial impact on the CTTS spectroscopy and dynamics of I -in this solvent. In this study, we have isolated "counterion-free" I -in THF by complexing the Na + counterion with 18-crown-6 ether. Ultrafast pump-probe experiments reveal that THF-solvated electrons (e THF -) appear 380 ( 60 fs following the CTTS excitation of "free" I -in THF. The absorption kinetics are identical at all probe wavelengths, indicating that the ejected electrons appear with no significant dynamic solvation but rather with their equilibrium absorption spectrum. After their initial appearance, ejected electrons do not exhibit any additional dynamics on time scales up to ∼1 ns, indicating that geminate recombination of e THF -with its iodine atom partner does not occur. Competitive electron scavenging measurements demonstrate that the CTTS excited state of I -in THF is quite large and has contact with scavengers that are several nanometers away from the iodide ion. The ejection time and lack of electron solvation observed for I -in THF are similar to what is observed following CTTS excitation of Na -in THF. However, the relatively slow ejection time, the complete lack of dynamic solvation, and the large ejection distance/lack of recombination dynamics are in marked contrast to the CTTS dynamics observed for I -in water, in which fast electron ejection, substantial solvation, and appreciable recombination have been observed. These differences in dynamical behavior can be understood in terms of the presence of preexisting, electropositive cavities in liquid THF that are a natural part of its liquid structure; these cavities provide a mechanism for excited electrons to relocate to places in the liquid that can be nanometers away, explaining the large ejection distance and lack of recombination following the CTTS excitation of I -in THF. We argue that the lack of dynamic solvation observed following CTTS excitation of both I -and Na -in THF is a direct consequence of the fact that little additional relaxation is required once an excited electron nonadiabatically relaxes into one of the preexisting cavities. In contrast, liquid water contains no such cavities, and CTTS excitation of I -in water leads to local electron ejection that involves substantial solvent reorganization.

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Photodetachment dynamics of closed-shell anions: Effects of perturbation by a strong neighboring dipole

Mondal

Bhattacharyya

2000

Int. J. Quantum Chem.

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Electron Photodetachment in Solution

Cited by 32 publications

References 0 publications

Electron Photodetachment from Aqueous Anions. 3. Dynamics of Geminate Pairs Derived from Photoexcitation of Mono- vs Polyatomic Anions

Electron Photodetachment from Aqueous Anions. 3. Dynamics of Geminate Pairs Derived from Photoexcitation of Mono- vs Polyatomic Anions

Ultrafast Charge-Transfer-to-Solvent Dynamics of Iodide in Tetrahydrofuran. 2. Photoinduced Electron Transfer to Counterions in Solution

Photodetachment dynamics of closed-shell anions: Effects of perturbation by a strong neighboring dipole

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