Stepwise Explosion of Atomic Clusters Induced by a Strong Laser Field

We present numerical simulations of a small Xe cluster exposed to strong laser pulses. Prompt ionization and fast acceleration of cluster electrons are followed by an explosion of the cluster ions. The explosion exhibits a shell structure, in which layers of cluster ions are expelled sequentially; the first ions expelled have kinetic energies $T_{\max }$ much higher than those encountered in Coulomb explosions of small molecules. These high energies are produced by the Coulomb energy of the original assembly of cluster ions, and by effective transfer of hot-electron energy to outer layers of the cluster. For laser intensities of ${10}^{15}\mathrm{W}/{\mathrm{cm}}^2$, $T_{\max }\approx 1\mathrm{keV}$ for ${\mathrm{Xe}}_{10}$ clusters.