Angular distributions of fragment ions of N(2) in a femtosecond laser field

We experimentally measure the kinetic energy and angular distributions of fragment ions of N(2) as a function of 820 nm femtosecond laser intensity. The angular dependence of fragments directly maps to the orbital symmetry of transient molecular ions. According to the observed energy and angular distribution of different charged fragment ions, reasonable fragmentation channels are proposed. Both the asymmetric channel ( 3, 1 ) and the symmetric channel ( 2, 2 ) are supposed to be generated directly from ( 2, 1 ) by different ionization mechanisms.