We study fragmentation processes induced by femtosecond laser pulses. Within an adiabatic treatment of the nuclear motion, the interaction with two identical but time-delayed pulses leads to interference structures in the momentum distribution which are related to the pulse delay. These structures are modified if an electronic degree of freedom is included in the wave-packet propagation. Additional time-dependent patterns are found in the electron momentum distributions which are also present for a single-pulse excitation. They are related to the delocalization of the electron density over the different charge centers. (C) 2011 Elsevier B.V. All rights reserved.