Solvent effects on the reactivity of solvated electrons with ions in isobutanol/water mixed solvents

Chen, Ruzhong; Avotinsh, Y.; Freeman, Gordon R.

doi:10.1139/v94-137

Cited by 34 publications

(21 citation statements)

References 15 publications

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“…In data recorded for a pHϭ0 purely aqueous solution ͑not shown͒, a rate constant for quenching of 2.8ϫ10 10 M Ϫ1 s Ϫ1 is obtained fitting with a single exponential and assuming pseudo-firstorder kinetics, which is in reasonable agreement with the reported value of 2.4ϫ10 10 M Ϫ1 s Ϫ1 . 56 The resonant detachment experiment was repeated in increasingly viscous solvents so that the role of the solvent environment on the iodide photodetachment dynamics could be determined. The solvent was varied from pure water ͓Fig.…”

Section: Methodsmentioning

confidence: 99%

The ejection distribution of solvated electrons generated by the one-photon photodetachment of aqueous I− and two-photon ionization of the solvent

Kloepfer

Vilchiz

Lenchenkov

et al. 2000

The Journal of Chemical Physics

194

362

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Articles you may be interested inOne-photon photodetachment of I − in glycerol: Spectra and yield of solvated electrons in the temperature range 329 T 536 K Mechanisms of the ultrafast production and recombination of solvated electrons in weakly polar fluids: Comparison of multiphoton ionization and detachment via the charge-transfer-to-solvent transition of Na − in THF The spectra and the relative yield of solvated electrons produced by resonant photodetachment of iodide anion in ethylene glycol in the temperature range 296T453 K Two-photon dissociation and ionization of liquid water studied by femtosecond transient absorption spectroscopyThe ultrafast dynamics following one-photon UV photodetachment of I Ϫ ions in aqueous solution are compared with those following two-photon ionization of the solvent. Ultrafast pump-probe experiments employing 50 fs ultraviolet pulses reveal similar and very rapid time scales for electron ejection. However, the electron ejection process from water pumped into the conduction band and from iodide ions detached at threshold are readily distinguishable. The observed picosecond timescale geminate recombination and electron escape dynamics are reconstructed using two different models, a diffusion-limited return of the electron from ϳ15 Å to its parent and a competing kinetics model governed by the reverse electron transfer rate. We conclude that the ''ejected'' electron in the halide detachment is merely separated from the halogen atom within the same solvent shell. The assignment of detachment into a contact pair is based on the recombination profile rather than by the postulate of any new spectral absorption due to an electron in a contact pair. The contact pair is surprisingly long-lived and the nonadiabatic recombination is rather slow considering the proximity of the partners. Experiments in mixed solvents confirm our assignment of the two distinct ejection mechanisms. The detachment mechanism is therefore fundamentally different in the resonant ͑one photon͒ charge-transfer-to-solvent ͑CTTS͒ process from the multiphoton detachment of aqueous iodide ions, which bears more similarity to the direct solvent ionization.

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Section: Methodsmentioning

confidence: 99%

The ejection distribution of solvated electrons generated by the one-photon photodetachment of aqueous I− and two-photon ionization of the solvent

Kloepfer

Vilchiz

Lenchenkov

et al. 2000

The Journal of Chemical Physics

194

362

View full text Add to dashboard Cite

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“…24 For the bulk bimolecular reaction H ϩ ϩe aq Ϫ at low ionic strength, the experimentally determined k s is 2.4ϫ10 10 M Ϫ1 s Ϫ1 . 28 Equation ͑4͒ seems well suited to describe the survival of electrons produced by the ionization of water, since ejection is on average long range and most electrons ''see'' the same solvent environment over their entire lifetime. The solid lines in Fig.…”

Section: B Time-resolved Electron Scavengingmentioning

confidence: 99%

Time-resolved scavenging and recombination dynamics from I:e− caged pairs

Kloepfer¹,

Vilchiz²,

Lenchenkov³

et al. 2002

The Journal of Chemical Physics

130

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The competition between geminate recombination of electrons with their parent radicals and electron scavenging with H+ is directly time resolved with ∼100 fs resolution at several acid concentrations. Electrons were produced from iodide photodetachment or two-photon ionization of H2O. With regards to those produced from iodide photodetachment, the separation between primary and secondary I:e− recombination is established using a full numerical solution to the diffusion equation. Electron ejection is found to be short range and a potential well of ∼3kbT depth stabilizing the solvent caged pair is required to yield a satisfactory fit to experiment. From time-resolved scavenging data up to 5 M HCl, it is shown that the electron can be scavenged both inside and outside the caged pair by H+ with nearly equal efficiency. The steady-state scavenging yield as a function of scavenger concentration is then predicted based on the determined time-dependent recombination function. Reassessment of several benchmark scavenging experiments from the 1960’s leads to the conclusion that the primary yield of electrons after excitation of iodide is near unity.

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“…Figure 7 shows the changes of k2/f with solvent composition for different solutes in tert-butanollwater mixtures at 298 K. The method described in ref. 13 was used to calculate k2/f for e; + (NHf,, + NO;,). The k2/f curves for different solutes are closer together than are the k2 curves in Table 2.…”

Section: LImentioning

confidence: 99%

Solvent effects on the reactivity of solvated electrons with ions in tert-butanol/water mixtures

Zhao¹,

Freeman²

1995

Can. J. Chem.

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Reactions of e; with the ions N H i V s , and H: showed different variations of rate with solvent composition in rerr-butanollwater mixtures from 0 to 100 mol% water. In pure rerr-butanol solvent at 298 K the respective values of k2 (lo6 m3 mol-I s-I) are 3.2, 13, and 42. The estimated value of reaction radius R, depends on the minimum number of solvent molecules needed between e; and the reactant ion to attain the static values of E of the bulk solvent used in the calculation of the Debye factor f ; R, is assumed to be larger in the alcohol-rich region than in the water-rich region, because the solvent molecules are larger. The Smoluchowski-Debye-Nernst-Einstein model is used to evaluate the effective reaction radius KR,, where K is the probability of reaction per encounter; KR, decreases from pure ferr-butanol to pure water. In the water-rich region the activation energies E2 of the efficient reactions, 11-24 kJ mol-I, are similar to EAo of the reactant electrolyes, 12-23 kJ mol-l. For the inefficient reactant NH: CIO;, E2 = 30 kJ mol-I. The high values of E2 = 43-53 kJ mol-I in pure rerr-butanol solvent are attributed to a high activation energy for diffusion of e; in this solvent.Ke.y words: rert-butanollwater solvents, solvated electron, ions, reactivity, solvent effects. RCsumC : Les vitesses de rtaction des e; avec les ions N H i T S et H l prtsentent des variationsdifferentes avec la composition des mtlanges de solvant rerr-butanolleau en allant de 0 B 100% en eau. Dans le tert-butanol pur, B 298 K, les valeurs relatives de k? (lo6 m h o l -I s-I) sont 3,2, 13 et 42.La valeur estimte du rayons de reaction R, dtpend du nombre minimal de moltcules de solvant requis entre le e; et I'ion rtactif pour atteindre les valeurs statiques de E de I'ensemble du solvant utiliste par le facteur f de Debye; comme les moltcules de solvant sont plus volumineuses que celles de I'eau, on considere que R, est plus Clevt dans la rtgion riche en alcool que dans la rtgion riche en eau. On a utilist le rnodttle de Smoluchowski-Debye-Nernst-Einstein pour tvaluer le rayon rtactionnelle efficace, KRI., dans lequel K est la probabilitt de rtaction par rencontre; KRr diminue en allant du rerr-butanol pur B l'eau pure.Dans la rtgion riche en eau, les energies d'activation E? des reactions efficaces, 11-24 kJ mol-l, sont semblables aux valeurs de EA0 des Clectrolytes qui rtagissent, 12-23 kJ mol-I. Pour le reactif inefficace N H ; CIO;, E? = 30 kJ mol-I. On attribue les valeurs tlevtes de E2 = 43-53 kJ rnol-' observtes dans le rerr-butanol B une Cnergie tlevte d'activation de la diffusion des e; dans ce solvant.

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Solvent effects on the reactivity of solvated electrons with ions in isobutanol/water mixed solvents

Cited by 34 publications

References 15 publications

The ejection distribution of solvated electrons generated by the one-photon photodetachment of aqueous I− and two-photon ionization of the solvent

The ejection distribution of solvated electrons generated by the one-photon photodetachment of aqueous I− and two-photon ionization of the solvent

Time-resolved scavenging and recombination dynamics from I:e− caged pairs

Solvent effects on the reactivity of solvated electrons with ions in tert-butanol/water mixtures

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