Unlocking the Double Bond in Protonated Schiff Bases by Coherent Superposition of S and S.

The primary event occurring during the E-to-Z photoisomerization reaction of retinal protonated Schiff base (rPSB) is single-to-double bond inversion. In this work we examine the nuclear dynamics that occurs when the initial excited state is a superposition of the S and S electronic excited states that might be created in a laser experiment. The nuclear dynamics is dominated by double bond inversion that is parallel to the derivative coupling vector of S and S. Thus, the molecule behaves as if it were at a conical intersection even if the states are nondegenerate.