Abstract

The protonated Schiff base of the 11-cis retinal (PSB11) is the chromophore of the visual pigment Rhodopsin (Rh). The biological activity of Rh is triggered by an ultrafast (200 fs) and efficient (0.65 quantum yield) light-induced cis-trans isomerization of PSB11 around the 11=12 double bond [1], which can be described as the ballistic motion of a photoexcited wavepacket from the Franck-Condon (FC) region through a conical intersection (CI) connecting the ground and excited electronic states. CIs are singularities on the potential energy surfaces (PES) that form a multi-dimensional ‘seam’ connecting the ground and excited states at isoenergetic points [2]. CIs are ubiquitous features in theoretical descriptions of organic photochemistry and are responsible for triggering radiationless decay and efficient and ultrafast conversion of photon energy into chemical energy.

© 2013 IEEE