Intensity and wavelength control of a single molecule reaction: Simulation of photodissociation of cold-trapped MgH ⁺

Photodissociation of cold magnesium hydride ions MgH+ leading to either Mg+ +H or Mg+ H+ is simulated from first principles. The purpose is to study the possibility of single molecule control of the products in the presence of two laser fields. The system evolves on four electronic potential-energy curves, X1 Σ, A1 Σ, B1 Π, and C1 Σ. These potential-energy curves are calculated from first principles using multireference self-consistent field theory. The accuracy of the electronic potential curves has been checked by calculating the energies of the rovibrational eigenstates and comparing them to experimental findings. The photodissociation dynamics has furthermore been simulated by solving the time-dependent Schrödinger equation. It is shown that the branching ratio of the two dissociation channels, Mg+ +H or Mg+ H+, can be controlled by changing the intensity and wavelength of the two driving laser fields.