Calculation of Absorption and Fluorescence Spectra of Large Polyatomic Molecules

The linear polyenes are a class of molecules whose spectroscopy, photophysics, and photochemistry have been a subject of active research, and are excellent candidates for illustrating the theory of non-Condon vibronic transitions. From various spectroscopic observations, it has been revealed that the linear (all-trans-)polyenes with four or more double bonds have two close-lying lowest singlet excited electronic states: the ionic ۱۱ Buelectronic state, and the covalent ۲۱Ag electronic state which lies lower than the ۱۱ Bu state.The transition from the ground state ۱۱ Ag to ۱۱ Bu state is strongly dipole allowed which leads to well-resolved absorption spectra, whereas to the ۲۱Ag state is symmetrically forbidden but vibronically allowed. In this study we present a general approach for calculating the Condon vibronic structure observed in electronic absorption and fluorescence spectra of all-trans-۱,۳,۵,۷-octatetraene.

کلیدواژه ها:

all-trans-۱ ، ۳ ، ۵ ، ۷-Octatetraene ، Condon vibronic structure ، Normal fluorescence ، Absorption spectra.