Motion in an ultralong-range potential in cold-Rydberg-atom collisions

In a recent letter Li et al. [Phys. Rev. Lett. 94, 173001 (2005)] have studied experimentally the role of dipole-dipole interactions in the ionization of Rydberg atoms and the formation of a cold plasma. The authors associated their observations with atomic motion due to such interaction. In this work, we adapt the dynamical model proposed by De Oliveira et al. [Phys. Rev. Lett. 90, 143002 (2003)] based on a two atom interaction, which reproduce qualitatively well some experimental results observed by Li and co-workers. This comparison presents clear evidences of motion in such ultralong range potential between cold-Rydberg atoms, which may be important for some applications, as quantum computation.