Investigation of spectrum accuracy by MO calculation

Abstract

In photo-excitation and -deexcitation of a molecule, it is very important to consider the change of occupied molecular orbitals between ground and excited states. Meanwhile, the vibrational structure is another important factor. In the current study, we calculated both molecular orbitals for electrons and nuclear vibrational spectra based on Franck-Condon principle using density functional method. In Franck-Condon calculation, we used zeroth order approximation of electronic transition dipole moment in excited states. The target of current study is an aromatic molecule which has a fused ring system containing nitrogen and quinone structure. We resolved absorption and emission spectra using molecular orbital functions including vibrational structures between ground and excited states. In our works, we calculated fluorescence spectrum in emission process. And in comparison of computed and experimental results, good reproducibilities of the waveform in both spectra were obtained. In addition, we obtained high reproducibility in emission intensity.