Biswas, Nandita ; Abraham, Becky ; Umapathy, Siva (2002) Investigation of short-time isomerization dynamics in p-nitroazobenzene from resonance Raman intensity analysis The Journal of Physical Chemistry A, 106 (41). pp. 9397-9406. ISSN 1089-5639
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Official URL: http://pubs.acs.org/doi/abs/10.1021/jp0108162
Related URL: http://dx.doi.org/10.1021/jp0108162
Abstract
Resonance Raman (RR) spectra are presented for p-nitroazobenzene dissolved in chloroform using 18 excitation wavelengths, covering the region of 1(n → π*) electronic transition. Raman intensities are observed for various totally symmetric fundamentals, namely, C-C, C-N, N=N, and N-O stretching vibrations, indicating that upon photoexcitation the excited-state evolution occurs along all of these vibrational coordinates. For a few fundamentals, interestingly, in p-nitroazobenzene, it is observed that the RR intensities decrease near the maxima of the resonant electronic 1(n→π*) transition. This is attributed to the interference from preresonant scattering due to the strongly allowed 1(π → π*) electronic transition. The electronic absorption spectrum and the absolute Raman cross section for the nine Franck-Condon active fundamentals of p-nitroazobenzene have been successfully modeled using Heller's time-dependent formalism for Raman scattering. This employs harmonic description of the lowest energy 1(n → π*) potential energy surface. The short-time isomerization dynamics is then examined from a priori knowledge of the ground-state normal mode descriptions of p-nitroazobenzene to convert the wave packet motion in dimensionless normal coordinates to internal coordinates. It is observed that within 20 fs after photoexcitation in p-nitroazobenzene, the N=N and C-N stretching vibrations undergo significant changes and the unsubstituted phenyl ring and the nitro stretching vibrations are also distorted considerably.
Item Type: | Article |
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Source: | Copyright of this article belongs to American Chemical Society. |
ID Code: | 64965 |
Deposited On: | 15 Oct 2011 12:37 |
Last Modified: | 15 Oct 2011 12:37 |
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