We present a non-adiabatic molecular dynamics simulation of a Na-2(+) molecule embedded in a single shell solvent made of 17 Ar atoms. The simulation is based on first principles calculation for 1-electron system combined with Tully surface hopping algorithm. The system is promoted to the first excited state and then followed during the first 10 ps. The dynamics can be divided into three temporal stages. First, the excess energy is quickly carried out by the Ar atoms aligned with the molecular axis. Second, during the 2 first picosecond, the Na-2(+) molecule expands and surface hopping takes place. Finally, the system enters a chaotic stage, which determines the issue of the dynamics. Recombination of Na-2(+) with almost complete evaporation of the solvent atoms occurs for 25% of the trajectories. Dissociation occurs otherwise, leading to the formation of small Na+Arp clusters, with an average value (p) over bar = 6. (C) 2009 Elsevier B.V. All rights reserved.