Coherent control of coupled field-nuclei-electron dynamics in strong field molecular ionization

Similar to the notion of adiabaticity with regard to the motion of electrons following nuclei, one can consider the adiabaticity of electrons following the variation of an applied electric field. Here we consider a competition between these two types of nonadiabatic electron dynamics in the resonance-enhanced strong-field ionization of a polyatomic molecule. We drive the molecules with a chirped ultrafast laser pulse whose frequency varies with time. The strong field of the laser pulse can drive Stark-shifted multiphoton resonance enhancement of the ionization, with the chirp of the pulse determining exactly when the multiphoton resonance occurs. This creates an opportunity for the molecule to undergo internal conversion before ionization, causing the molecule to reach different states of the molecular cation. We interpret our measurements using strong-field ionization dynamics calculations, which include multiphoton resonance, dynamic Stark shifts, as well as vibrational dynamics and internal conversion during the ionization process. Together, the measurements and calculations demonstrate how the light matter coupling can compete with the coupled motions of electrons and nuclei in strong-field laser-molecule interactions and offers control over the final state of the molecular cation.