We study theoretically diatomic molecules which are prepared in a superposition of quasibound resonance states by a femtosecond laser pulse. An analytical (Landau–Zener-like) result is derived for the momentum distribution of the atomic fragments in the asymptotic force-free region after a single passage of a curve crossing. Furthermore, at later times, simple analytical expressions show how the emerging structures in the momentum distribution are related to the energies of the resonance states.