Quantum interference in double ionization and fragmentation of C(6)H(6) in intense laser fields.

During tunnel ionization of atoms or molecules by strong laser fields, the electron acquires a transverse velocity which is characteristic of the ionization process. Ellipticity measurements identify nonsequential double ionization as due to recollision in C(6)H(6) and simultaneously measure the transverse velocity distribution of the electron wave packet. We observe signatures of quantum interference of different tunneling trajectories and find identical dependence of nonsequential double ionization and fragmentation of C(6)H(6) on the ellipticity of the laser polarization. This identifies electron recollision as the dominant source of fragmentation at 1.4 microm.