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TRANSPORT OF EXCITATION-ENERGY IN A DOPED MOLECULAR AGGREGATE .3. NUMERICAL INVESTIGATION OF EXCITON HOPPING WITH VARIOUS EXCITON-DEPLETING PROCESSES

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Title TRANSPORT OF EXCITATION-ENERGY IN A DOPED MOLECULAR AGGREGATE .3. NUMERICAL INVESTIGATION OF EXCITON HOPPING WITH VARIOUS EXCITON-DEPLETING PROCESSES
 
Creator DATTA, SN
PRABHU, NV
 
Subject crystal
impurities
 
Description A brute-force numerical investigation has been carried out on the hopping of excitons in a three-dimensional molecular aggregate. Possibilities of vibronic decay, rapid chemical reactions of saturated species, radiative decay of overpopulated molecules, and cooperative chemical reactions involving saturated exciton populations on traps of two different types have been considered. Investigations have been performed with two types of initial distribution of excitons-facial and random-and for 10,000 or, sometimes, for 20,000 time steps each of duration 1 ps. Several interesting observations have been made from this computer experiment: (1) The total number of occurrences of fast reactions depends upon the initial distribution of excitons. (2) It decreases if other exciton depleting processes are at work. (3) It also depends on the pattern of placement of traps. (4) The location of impurities also affects the rate of occurrence of these reactions. Thus, more reactions occur when the excitons are initially concentrated on one face and traps are suitably located on the path of flow of these excitons. A random initial distribution tends to equilibrate the excitons quickly over all the lattice points, thus giving rise to fewer reactions. (5) The number of reactions need not necessarily increase with the number of reaction centers; in fact, it decreases as more centers are added when the supply of excitons is severely limited. (6) A complicated dynamics results when different types of additional processes, viz., enhanced fluorescence, radiative emissions, and cooperative chemical reactions are simultaneously allowed. The cooperative process has been clearly found to dominate. A first-order rate constant of about 10(8) s-1 has been calculated for the occurrence of the cooperative process. This rate is affected when other nonconserving processes are switched on. Observations (1), (4), and (5) are the most important conclusions of our work. They lie outside the scope of traditional models such as the random walk model, the diffusion model, and the lattice model for the migration of excitons in a molecular aggregate.
 
Publisher JOHN WILEY & SONS INC
 
Date 2011-08-16T16:58:31Z
2011-12-26T12:55:03Z
2011-12-27T05:43:35Z
2011-08-16T16:58:31Z
2011-12-26T12:55:03Z
2011-12-27T05:43:35Z
1993
 
Type Article
 
Identifier INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, 46(2), 295-317
0020-7608
http://dx.doi.org/10.1002/qua.560460206
http://dspace.library.iitb.ac.in/xmlui/handle/10054/9563
http://hdl.handle.net/10054/9563
 
Language en