Optimal control approach to suppression of radiationless transitions.

We propose a general approach for eliminating radiationless transitions in polyatomic molecules and illustrate it through the example of the S2-->S1 internal conversion of pyrazine. Essential to our approach is the phenomenon of electronically localized eigenstates of strongly vibronically coupled Hamiltonians. The occurrence of such states, observed here for the first time, and its generality are traced to the origin of scars of periodic orbits.