Dissociation pathways established in strong-field single ionization of molecular CO

In this study, we present the dissociative single ionization of CO molecules in strong laser field by measuring the time-of-flight mass spectra of the dissociative fragment C ^+ with different laser intensities and polarization directions, respectively. The results indicate that the molecular ion CO ^+ produced by over-the-barrier ionization can be populated in not only the ground X^2Σ ^+ state, but also the next two lower-lying electronic A^2 and B^2Σ ^+ states. By evaluation of the potential energy curves, we assign the multi-peak structure of the time-of-flight spectra for ion fragment C ^+ to the dissociation of the vibrational states of two excited A^2 and B^2Σ ^+ states via the dissociation pathways |A^2 -0ω⟩→ |D^2 -4ω⟩ , |B^2Σ ^+-0ω⟩→ |3^2 -3ω⟩ , and |B^2Σ ^+-0ω⟩→ |3^2Σ ^+-3ω⟩ . The results imply that the dissociation pathway of molecular cations can be selected using pump-probe technology via accurately tuned laser parameters.