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-2 Sigma(+) state, but also the next two lower-lying electronic A(2)Pi and B-2 Sigma(+) 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)Pi and B-2 Sigma(+) states via the dissociation pathways vertical bar A(2)Pi - 0 omega > -> vertical bar D-2 Pi - 4 omega >, vertical bar B-2 Sigma(+) - 0 omega > -> vertical bar 3(2)Pi - 3 omega >, and vertical bar B-2 Sigma+ - 0 omega > -> vertical bar 3(2)Sigma(+) - 3 omega >. The results imply that the dissociation pathway of molecular cations can be selected using pump-probe technology via accurately tuned laser parameters.