In an intermediate range of light-molecule interaction strength, the molecular electronic structure is more or less retained, but the energy levels are shifted through the Stark effect. As the shifts are proportional to the states' polarizability, they can vary from essentially nil for the ground state to free electron-like for high Rydberg states, giving rise to characteristic transient resonances in a pulsed light field. Stark shifting of electronic states has been proposed by Stolow and coworkers as a general method for exerting control over chemical reactions. In this dynamic Stark control scheme, a non-resonant control pulse is employed to manipulate the evolution of a molecular wavepacket, either by modulating the initial conditions or a critical coupling between states en route to reaction product formation.
In the talk I will present results from exploration of a different scheme of chemical reaction control through the dynamic Stark effect. At intermediate strengths of light-molecule interaction, a single laser pulse may be used to reshape potential energy curves of electronic states that possess mixed Rydberg-valence character and thus affect the course of a photochemical reaction. The dynamic Stark effect is proportional to the laser intensity, which provides a convenient control parameter on the extent of the potential reshaping and reaction outcome. Calculations on the photodissociation of O2 in the electronic states responsible for the atmospherically very important Schumann-Runge absorption band indicate that good control of the product channel branching might be attained with this scheme.