Theoretical studies on the vibrationally-resolved absorption and fluorescence spectra of H-Pyrene+ and H-Coronene+

H-Pyrene and H-Coronene are important carrier candidates for the diffuse interstellar band. In order to understand the observed absorption and fluorescence emission spectra of H-Pyrene and H-Coronene, time-dependent density functional theory (TD-DFT) method and Franck-Condon approximation have been employed to simulate the corresponding vibrationally-resolved optical spectra. For H-Pyrene, the calculated absorption, emission and 0-0 band energies are in good agreement with the experimental values. The strong absorption and emission vibrational peaks near the 0-0 band match well with the experiment peaks. A noticeable deviation for several weak peaks far away from the origin band is observed, as a result of the vibronic coupling with other excited states. For H-Coronene, the predicted vibrationally resolved electronic absorption and emission spectra resemble very well their experimental counterparts spectra, allowing to fully assign the observed vibronic peaks. (C) 2015 Elsevier B.V. All rights reserved.