Quantum Control of the Dynamical Behavior of Resonance States in Small Organic Molecules With Intense Fields

A new quantum control scheme is suggested to modify the final fragment distribution produced upon decay of a resonance state. The scheme is applied to the electronic predissociation of CH 3 starting from two different resonances. After using a weak pump pulse to excite the resonance, a moderately intense control field is applied, which has the effect (in the Floquet representation) of shifting upwards the ground electronic state by an energy equivalent to the photon energy of the control pulse. For appropriate excitation energies the shifted ground state crosses some of the excited states, and generates light‐induced conical intersections with those radiatively coupled to it. Also, in the absence of crossings, the radiative couplings between the ground and the excited states act as intense nonadiabatic couplings (NACs) upon application of the control field. These light‐induced NACs reshape the potential‐energy landscape of all the electronic states, opening new pathways for population transfer between them, what allows to modify the fragment distribution, and also the resonance lifetime. A large degree of control is achieved. Experimental implementation of the scheme is straightforward, and its application to photodissociation processes mediated by resonances in a large variety of organic molecules appears universal.