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Absorption and resonance Raman spectroscopy of the 1Bu state of trans-1,3,5-hexatriene including vibronic coupling



The vibronic coupling between the first excited S1 (21Ag) and the second excited S2 (11Bu) singlet electronic states in spectroscopy of trans-1,3,5-hexatriene molecule is investigated on the basis of a model consisting of two electronic states coupled by two vibrational modes. Employing a perturbation theory that treats the intramolecular couplings in a perturbative manner, the absorption and resonance Raman cross sections and excitation profiles of this molecule are calculated using the time-correlation function formalism. The non-Condon corrections are included in evaluation of cross sections. The multidimensional time-domain integrals that arise in these calculations have been evaluated for the case in which S0 (11Ag)[BOND]S2 (11Bu) electronic transition takes place between displaced and distorted harmonic potential energy surfaces. The calculated spectra are in good agreement with the experimental ones. Copyright © 2011 John Wiley & Sons, Ltd.