Vibrationally resolved UV/Vis spectroscopy with time-dependent density functional based tight binding

We report a time-dependent density functional based tight-binding (TD-DFTB) scheme for the calculation of UV/Vis spectra, explicitly taking into account the excitation of nuclear vibrations via the adiabatic Hessian Franck-Condon method with a harmonic approximation for the nu- clear wavefunction. The theory of vibrationally resolved UV/Vis spectroscopy is rst summarized from the viewpoint of TD-DFTB. The method is benchmarked against time-dependent density functional theory (TD-DFT) calculations for strongly dipole allowed excitations in various aro- matic and polar molecules. Using the recent 3ob:freq parameter set of Elstner’s group, very good agreement with TD-DFT calculations using local functionals was achieved.