Abstract
The vibrational structure of the T1 resonance Raman spectra of β-ionylidene acetaldehyde (C15 aldehyde) and retinal are analyzed with the help of semiempirical quantum chemical calculations. The T1 equilibrium structures and vibrational force fields, along with the structure in the Tn state which is in resonance with the exciting wavelength, are obtained and employed to model the spectra under the assumption of a dominant Franck–Condon mechanism.