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Interfacial Charge-Transfer Absorption: Semiclassical Treatment

Creutz, Carol and Brunschwig, Bruce S. and Sutin, Norman (2005) Interfacial Charge-Transfer Absorption: Semiclassical Treatment. Journal of Physical Chemistry B, 109 (20). pp. 10251-10260. ISSN 1520-6106. doi:10.1021/jp050259+.

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Optically induced charge transfer between adsorbed molecules and a metal electrode was predicted by Hush to lead to new electronic absorption features but has not been experimentally observed. However, Gerischer characterized photocurrents arising from such absorption between adsorbed metal atoms and semiconductor conduction bands. Interfacial charge-transfer absorption (IFCTA) provides information concerning the barriers to charge transfer between molecules and the metal/semiconductor and the magnitude of the electronic coupling and could thus provide a powerful tool for understanding interfacial charge-transfer kinetics. Here we provide a framework for modeling and predicting IFCTA spectra. The key feature of optical charge transfer to or from a band of electronic levels (taken to have a constant density of states and electronic coupling element) is that the absorption probability reaches half intensity at λ + ΔG^θ, where λ and ΔG^θ are the reorganization energy and free-energy gap for the optical charge transfer, attains >90% intensity at λ + ΔG^θ + 0.9 √4λk_BT, and remains essentially constant until the top (bottom) level of the band is attained. However, when the electronic coupling and transition moment are assumed to be independent of photon energy (Mulliken−Hush model), a peaked, highly asymmetric absorption profile is predicted. We conclude that, in general, the electronic coupling between molecular adsorbates and the metal levels is so small that absorption is not detectable, whereas for semiconductors there may be intense features involving coupling to surface states.

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Brunschwig, Bruce S.0000-0002-6135-6727
Additional Information:© 2005 American Chemical Society. Received: January 14, 2005; In Final Form: March 29, 2005. Publication Date (Web): April 28, 2005. This research was carried out at Brookhaven National Laboratory under contract DE-AC02-98CH10886 with the U.S. Department of Energy, supported by its Division of Chemical Sciences, Office of Basic Energy Sciences, and at the California Institute of Technology by the Arnold and Mabel Beckman Foundation. We thank S. Feldberg for providing the program enabling the calculation of Figure 7 and S. Lymar, M. D. Newton, and M. Spitler for helpful discussions. This article was posted ASAP on the Web on 4/28/2005. A change was made in the paragraph preceding eq 33. The correct version was posted on 5/02/2005.
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Department of Energy (DOE)DE-AC02-98CH10886
Arnold and Mabel Beckman FoundationUNSPECIFIED
Issue or Number:20
Record Number:CaltechAUTHORS:20170524-095235031
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Official Citation:Interfacial Charge-Transfer Absorption:  Semiclassical Treatment Carol Creutz, Bruce S. Brunschwig, and Norman Sutin The Journal of Physical Chemistry B 2005 109 (20), 10251-10260 DOI: 10.1021/jp050259+
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:77704
Deposited By: Tony Diaz
Deposited On:24 May 2017 17:01
Last Modified:15 Nov 2021 17:33

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