dorsal/arxiv
View SchemaElectron Photodetachment from Aqueous Anions. II. Ionic Strength Effect on Geminate Recombination Dynamics and Quantum Yield for Hydrated Electron
| Authors | Myran C. Sauer, Jr., Ilya A. Shkrob, Rui Lian, Robert A. Crowell, David M. Bartels, Stephen E. Bradforth |
|---|---|
| Categories | |
| ArXiv ID | physics/0404056 |
| URL | https://arxiv.org/abs/physics/0404056 |
| DOI | 10.1021/jp047435j |
Abstract
In concentrated solutions of NaClO4 and Na2SO4, the quantum yield for free electron generated by detachment from photoexcited anions (such as I-, OH-, ClO^4-, and [SO3]^2-) linearly decreases by 6-12% per 1 M ionic strength. In 9 M sodium perchlorate solution, this quantum yield decreases by roughly an order of magnitude. Ultrafast kinetic studies of 200 nm photon induced electron detachment from Br-, HO- and [SO3]^2- suggest that the prompt yield of thermalized electron does not change in these solutions; rather, the ionic strength effect originates in more efficient recombination of geminate pairs. Within the framework of the recently proposed mean force potential (MFP) model of charge separation dynamics in such photosystems, the observed changes are interpreted as an increase in the short-range attractive potential between the geminate partners. Association of sodium cation(s) with the electron and the parent anion is suggested as the most likely cause for the observed modification of the MFP. Electron thermalization kinetics suggest that the cation associated with the parent anion (by ion pairing and/or ionic atmosphere interaction) is passed to the detached electron in the course of the photoreaction. The precise atomic-level mechanism for the ionic strength effect is presently unclear; any further advance is likely to require the development of an adequate quantum molecular dynamics model.
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"date_created": "2026-03-02T18:00:49.890000Z",
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"abstract": "In concentrated solutions of NaClO4 and Na2SO4, the quantum yield for free\nelectron generated by detachment from photoexcited anions (such as I-, OH-,\nClO^4-, and [SO3]^2-) linearly decreases by 6-12% per 1 M ionic strength. In 9\nM sodium perchlorate solution, this quantum yield decreases by roughly an order\nof magnitude. Ultrafast kinetic studies of 200 nm photon induced electron\ndetachment from Br-, HO- and [SO3]^2- suggest that the prompt yield of\nthermalized electron does not change in these solutions; rather, the ionic\nstrength effect originates in more efficient recombination of geminate pairs.\nWithin the framework of the recently proposed mean force potential (MFP) model\nof charge separation dynamics in such photosystems, the observed changes are\ninterpreted as an increase in the short-range attractive potential between the\ngeminate partners. Association of sodium cation(s) with the electron and the\nparent anion is suggested as the most likely cause for the observed\nmodification of the MFP. Electron thermalization kinetics suggest that the\ncation associated with the parent anion (by ion pairing and/or ionic atmosphere\ninteraction) is passed to the detached electron in the course of the\nphotoreaction. The precise atomic-level mechanism for the ionic strength effect\nis presently unclear; any further advance is likely to require the development\nof an adequate quantum molecular dynamics model.",
"arxiv_id": "physics/0404056",
"authors": [
"Myran C. Sauer, Jr.",
"Ilya A. Shkrob",
"Rui Lian",
"Robert A. Crowell",
"David M. Bartels",
"Stephen E. Bradforth"
],
"categories": [
"physics.chem-ph",
"physics.optics"
],
"doi": "10.1021/jp047435j",
"title": "Electron Photodetachment from Aqueous Anions. II. Ionic Strength Effect on Geminate Recombination Dynamics and Quantum Yield for Hydrated Electron",
"url": "https://arxiv.org/abs/physics/0404056"
},
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