Crossover from Dispersive to Diffusive Energy Transport

  • T. Kirski
  • C. von Borczyskowski
Part of the NATO ASI Series book series (NSSB, volume 258)


Excitation energy transport in disordered solids is one of the relaxation phenomena studied intensively during the past ten years. Especially transport in glasses has attracted considerable interest1, but also some porous systems2, polymers3 and disordered crystals4 have been investigated. Disordered crystals offer the possibility to model complex relaxation behavior in a distinct and well-defined manner. For this reason we have chosen a chemically mixed crystal (CMC) of p-dichloro-(DCB) in p-dibromobenzene (DBB) as a representative example of a substitutionally disordered crystal. In recent publications we have shown that triplet excitation energy transport exhibits dispersive character5 as a function of doping concentration. Instead of using isotopically mixed crystals6 CMC show due to the formation of induced energy funnels7, 8 a richer energy landscape which gives rise to a broad waiting time distribution for jumps of excitation energy described by random walk processes9. Phosphorescence measurements indicated10 that at temperatures above about 6 K transport becomes strongly temperature dependent. This gave rise to a comparison of transport in disordered crystals with relaxation processes in spin glasses11. Within this concept energy transport exhibits as a function of temperature a kind of glass transition which is manifested in a cross-over from ergodic to non-ergodic behavior11. Above the glass transition, the phosphorescence decay of the excitation energy can be described by a stretched exponential Kohlrausch-Williams-Watts (KWW) behavior. In this communication we like to report on the temperature dependence of the parameters β and τ, which enter the KWW description via the phosphorescence intensity IPhos, ~exp[-(t/τ)β].


Random Walk Spin Glasses11 Energy Transport Energy Separation Phosphorescence Intensity 
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  1. 1.
    A. Blumen, J. Klafter and G. Zumofen, in: “Optical Spectroscopy of Glasses”, I. Zschokke, ed., Reidel, Dordrecht (1986)Google Scholar
  2. 2.
    J. Prasad and R. Kopelman, Phys. Rev. Lett. 59:2103 (1987)CrossRefGoogle Scholar
  3. 3.
    G. Peter, H. Bassler, W. Schrof and H. Port, Chem. Phys. 94:445Google Scholar
  4. 4.
    G. B. Talapatra, D. N. Rao and P. N. Prasad, Chem. Phys. 101:147Google Scholar
  5. 5.
    T. Kirski, J. Grimm and C. von Borczyskowski,.T. Chem. Phys. 87:2062 (1987)Google Scholar
  6. 6.
    R. Kopelmann, in: “Laser Spectroscopy of Solids”, W. M. Yen and P. Selzer, eds., Springer Verlag, Berlin (1981)Google Scholar
  7. 7.
    J. Grimm, T. Kirski and C. von Borczyskowski, Chem. Phys. Lett. 128:569 (1986)CrossRefGoogle Scholar
  8. 8.
    J. Kolenda and C. von Borczyskowski, J. Luminesc. 42:217 (1988)CrossRefGoogle Scholar
  9. 9.
    C. von Borczyskowski and T. Kirski, Phys. Rev. Lett. 60:1578 (1988)CrossRefGoogle Scholar
  10. 10.
    C. von Borczyskowski and T. Kirski, J. Luminesc. 38:295 (1987)CrossRefGoogle Scholar
  11. 11.
    C. von Borczyskowski and T. Kirski, Phys. Rev. B 40:11335 (1989)CrossRefGoogle Scholar
  12. 12.
    C. von Borczyskowski, M. Plato, P. Dinse and K. Mobius, Chem. Phys. 35:355 (1978)CrossRefGoogle Scholar
  13. 13.
    S. A. Gilbert, T. Kirski, H. Brenner and C. von Borczyskowski, Chem. Phys. Lett., subm.Google Scholar
  14. 14.
    C. von Borczyskowski and T. Kirski, Ber. Buns. Gesell. Phys. Chem. 93:1373 (1989)CrossRefGoogle Scholar
  15. 15.
    C. von Borczyskowski, in: “Relaxation in Complex Systems and Related Topics”, I. A. Campbell and C. Giovanella, eds., Plenum Press, New York (1989)Google Scholar
  16. 16.
    M. D. Fayer and C. R. Gochanour, J. Chem. Phys. 65:2472 (1976)Google Scholar

Copyright information

© Plenum Press, New York 1991

Authors and Affiliations

  • T. Kirski
    • 1
  • C. von Borczyskowski
    • 1
  1. 1.Fachbereich PhysikFreie Universität BerlinBerlin 33Germany

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