| Abstract
| - Time-dependent density functional theory (TDDFT) is applied to calculate vertical excitation energies oftrans-1,3-butadiene, trans−trans-1,3,5-hexatriene, all-trans-1,3,5,7-octatetraene, and all-trans-1,3,5,7,9-decapentaene. Attachment and detachment densities for transitions in butadiene and decapentaene from theground state to the 2 1Ag and 1 1Bu excited states are also calculated and analyzed. Based on comparisonswith experimental results and high level ab initio calculations in the literature, significant improvement overconfiguration−interaction singles is observed for the 2 1Ag state of the polyenes, which has been known tohave significant double excitation character. For the 1 1Bu state, TDDFT underestimates the excitation energyby 0.4−0.7 eV. In this case we have observed a significant difference between the results for TDDFT andTDDFT within the Tamm−Dancoff approximation, both in excitation energies and, at least for butadiene, inthe character of the excited state.
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