Studies of the Ground and Excited-State Surfaces of the Retinal Chromophore using CAM-B3LYP

The isomerization of the 11-cis isomer (PSB11) of the retinal chromophore to its all-trans isomer (PSBT) is examined. Optimized structures on both the ground state and the excited state are calculated, and the dependence on torsional angles in the carbon chain is investigated. Time-dependent density functional theory is used to produce excitation energies and the excited-state surface. To avoid problems with the description of excited states that can arise with standard DFT methods, the CAM-B3LYP functional was used. Comparing CAM-B3LYP with B3LYP results indicates that the former is significantly more accurate, as a consequence of which detailed cross sections of the retinal excited-state surface are obtained.