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SPECTROSCOPIC STUDIES OF PHOTOCHEMICALLY INDUCED ENERGY TRANSFER IN VAN DER WAALS $MOLECULES^{a}$

By Murthy S. Gudipati

Abstract

[1] Wagner, R., Schouren, F., and Gudipati, M. S.; Journal of Physical Chemistry, A. 104, 3593, 2000. $^{a}$ The Author thanks his former students Dr. Martin Kalb, Dr. Robert Wagner, Dr. Andreas Klein and Dr. Frank Schouren for their scientific contribution at the University of Cologne, where the experiments have been carried out. $^{b}$ on leave from University of Cologne, GermanyAuthor Institution: IPST, University of Maryland, College Park, MD 20742; Visiting Scientist at Molecular Physics Laboratory, SRI International, Menlo Park, CA, 94025 (email: murthy.gudipati@sri.com).Energy transfer plays an important role in a wide variety of processes, spanning from biological to atmospheric in nature. Most of the commonly encountered energy transfer processes can be understood in terms of near-resonant transition dipole induced (F\""{o}rster type) or electron exchange (Dexter type) mechanisms. However, there have been rare examples of energy transfer, where the resonance criterion has severely been violated. In such cases a variety of terminologies have been used to identify these energy transfer processes. A common aspect among the different postulates is the encounter of the energy donor $(D^{\ast})$ and energy acceptor (A) species below the van der Waals separation. We have discovered such an energy transfer process in van der Waals $O\cdots CO$ molecules, which have been generated through vacuum ultraviolet photolysis of $CO_{2}$ in rare-gas matrices using synchrotron radiation [1]. Electronic excitation of CO in the $O\cdots CO$ species leads to the formation of excited $CO_{2}$, which dissociates to excited O and ground-state CO in the $O\cdots CO$ species. As the first half of this process is photochemical formation of $CO_{2}$, we named this process as ``photochemically induced energy transfer'', whose general form of mechanism is: $D^{\ast} + A \to (DA)^{\ast}\rightarrow D + A^{\ast}$, where $^{\ast}$ represents the localization of excitation. Photochemically induced energy transfer (a) need not be a resonant process, like F\""{o}rster or Dexter type processes, (b) there need be no spin-selection rules to be fulfilled nor the total spin angular momentum to be conserved. Examples of photochemically induced energy transfer and other energy transfer processes in van der Waals molecules/complexes generated and stabilized in rare-gas matrices will be presented

Publisher: 'The Ohio State University Libraries'
Year: 2002
OAI identifier: oai:kb.osu.edu:1811/20337
Provided by: KnowledgeBank at OSU
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