Resonance Raman study of the solvent dynamics for ultrafast charge transfer transition in 4-nitro-4'-dimethylamino-azobenzene

Biswas, Nandita ; Umapathy, Siva (2003) Resonance Raman study of the solvent dynamics for ultrafast charge transfer transition in 4-nitro-4'-dimethylamino-azobenzene The Journal of Chemical Physics, 118 (12). pp. 5526-5536. ISSN 0021-9606

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Official URL: http://jcp.aip.org/resource/1/jcpsa6/v118/i12/p552...

Related URL: http://dx.doi.org/10.1063/1.1555628

Abstract

Contribution of solvent reorganization energy is known to be significant for ultrafast charge transfer processes, when the solvent relaxation times are slower than the rate of charge transfer. In this paper, we show that from resonance Raman intensities of a charge transfer transition in combination with Heller,s time-dependent wave packet approach and Brownian oscillator model, one can have a reasonable estimate for the different types of solvent (inertial as well as diffusive) and vibrational reorganization energies. Resonance Raman spectra have been recorded for 4-nitro-4'-dimethylamino-azobenzene (DA) that undergoes photoinduced charge transfer transition, in acetonitrile and benzonitrile. In the two solvents, the total solvent reorganization energy is partitioned into its inertial and diffusive components from the available information on their relaxation time scales. Thus, partitioning of the solvent reorganization energy reveals the importance of the extent of contribution of the two components to the charge transfer rates. The short time dynamics of DA in the two solvents is then examined from a priori knowledge of the ground state normal modes in order to convert the wave packet motion in dimensionless displacements to internal coordinates. The dynamics in DA infers that within 20 fs after photoexcitation from the ground to the charge transfer state, the excited state evolution occurs along N-O, N-N, C-N, and C-C stretching vibrations.

Item Type:Article
Source:Copyright of this article belongs to American Institute of Physics.
Keywords:Organic Compounds; Raman Spectra; Solvent Effects; Charge Exchange; Vibrational States; Ground States
ID Code:64960
Deposited On:15 Oct 2011 12:37
Last Modified:15 Oct 2011 12:37

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