Optical absorption spectra of V+4 isomers:: One example of first-principles theoretical spectroscopy with time-dependent density functional theory

We have calculated the optical absorption spectrum of four isomers of the ionized Vanadium tetramer V-4(+) using the time-dependent density functional theory, with the adiabatic local density approximation for the exchange and correlation potential. The computational scheme is based on a real-time propagation of the time-dependent Kohn-Sham equations. The significantly different spectra of the four isomers permit the identification of the isomer with C-2v symmetry as the one predominantly present in the laboratory beams. This assignment is confirmed by the fact that this isomer has the lowest energy. We also report other properties of these charged structures such as static electric dipole polarizabilities, vertical ionization potentials and electron affinities, and densities of electronic states.