Charge asymmetric dissociation induced by sequential and non-sequential strong field ionization

Summary form only given. For the first time with near-infrared radiation, we observe the charge asymmetric dissociation (CAD) of N(2,0) and O(2,0) using 30 fs 800 nm Ti:sapphire laser pulse. More significantly, unlike the previous observations in the soft X-ray and the UV, the N/sup 2+/ fragment has a slow kinetic energy release, which may indicate the CAD of N(2,0) is in the excited states. However, like the previous observations, the formation of N(2,0) involves a non-sequential vertical transition. But O(2,0) involves a non-vertical excitation process. Furthermore, the threshold intensity of these two channels is not enough to provide the dipole coupling to populate the CAD states. These results rule out the hypothesis of a dipole coupling to the charge transfer states, and provide evidence that CAD is the natural result of strong field excitation and ionization. Moreover, the quite different behavior of N(2,0) and O(2,0) has to be related to the different electronic structures of N/sub 2/ and O/sub 2/: N/sub 2/ has a closed shell electronic structure, while the outermost orbital (1/spl pi//sub g/)/sup 2/ of the ground state O/sub 2/ is only half filled. The detailed electronic structure can lead to different behaviors of molecules interacting with strong laser fields.