Stairway to the conical intersection: A computational study of the retinal isomerization

The density functional theory (DFT) calculations are used for studying the potential-energy surface of the first excited state of the 11-cis-retinal protonated Schiff base (PSB11) chromophore. The studies have suggested few reaction pathways on the potential-energy surface of the excited state leading toward the conical interaction and resulting in a cis to trans isomerization of the retinal chromophore.