Restricted open-shell Kohn-Sham theory for π-π* transitions.: I.: Polyenes, cyanines, and protonated imines

We present a self-consistent field algorithm for the restricted open-shell Kohn-Sham method which can be used to calculate excited states that have the same spatial symmetry as the corresponding ground states. The method is applied to pi-pi(*) transitions in polyenes, cyanines, and protonated imines. Excitation energies obtained with gradient corrected functionals are found to be significantly redshifted; the shift is constant within a homologous series. Planar excited state geometries have been optimized for all systems.(C) 2003 American Institute of Physics.