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The temperature dependence of the Amide I band of crystallline acetanilide

The temperature dependence of the Amide I band of crystallline acetanilide. Leonor Cruzeiro CCMAR and FCT, University of Algarve. The acetanilide (ACN) molecule. The ACN crystal. C J Brown and D E C Corbridge, Acta Cryst 7: 711 (1954). The ACN crystal (cont). One ACN plane.

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The temperature dependence of the Amide I band of crystallline acetanilide

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  1. The temperature dependence of the Amide I band of crystallline acetanilide Leonor Cruzeiro CCMAR and FCT, University of Algarve

  2. The acetanilide (ACN) molecule

  3. The ACN crystal C J Brown and D E C Corbridge, Acta Cryst 7: 711 (1954)

  4. The ACN crystal (cont)

  5. One ACN plane

  6. The Amide I band of ACN AC Scott, E Gratton, E.Shyamsunder and G. Careri, Phys Rev B 32: 5551 (1985)

  7. Generalized Davydov/Scott Model

  8. A more realistic interaction Hamiltonian?

  9. Crystal dynamics at finite temperature

  10. Absorption spectrum

  11. Calculated linear absorption spectrum Solid (T=10 K), dashed (T=80 K) and dotted (T=240 K).  = 40 pN.

  12. Calculated localization versus energy Solid (T=10 K), dashed (T=80 K) and dotted (T=240 K)

  13. Emission spectrum

  14. Calculated emission spectrum Solid (T=10 K), dashed (T=80 K) and dotted (T=240 K).  = 40 pN.

  15. Two different explanations • Previous: low energy peak comes self-trapped states, high energy peak from delocalized, free exciton states. • Present: low energy peak comes from strongly bonded ACN molecules, higher energy peak comes from weakly bonded (length, orientation) ACN molecules. Both peaks come from localized states, but none is self-trapped. • Previous: provides a quantitative description of the temperature dependence of the lower energy peak, but not of the higher energy one. • Present: provides a semi-quantitative description of the temperature dependence of the full linear absorption spectrum.

  16. Acknowledgements • Holly Freedman, Biophysics, CCMAR, UAlg. • Paulo Afonso Lopes, CITI, UNL. • Milipeia, University of Coimbra. • Partial support from the Portuguese Foundation for Science and Technology (FCT, Portugal) is acknowledged.

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