N-body simulation of nanoplasmas

The irradiation of atomic or molecular clusters with ultraintense lasers can induce the formation of hot completely ionized nanoplasmas, which rapidly expand into a vacuum, as predicted by Dawson. The physics of the expansion of these nanoplasmas, composed by 102 104 positive ions and electrons, has been extensively studied under a variety of conditions, using different analytical and numerical approaches, based upon fluid or kinetic models. A rigorous analysis of the dynamics of nanoplasmas is presented here by using the N-body simulation method and comparing the results with reference solutions for the collisionless kinetic equations, obtained using the shell model [1], which is a gridless, particle-based algorithm. The analysis is carried out comparing ensemble averages in order to take into account different initial conditions of the system. Two test cases, the electron dynamics in the initial phase of the expansion and the formation of shock shells during Coulomb explosion have been considered. For the electron dynamics in the initial phase of the expansion, the results indicate that the collisionless kinetic model is in good agreement with the N-body simulation, as far as mean values are considered; however, in a single experiment the calculated values may differ significantly from the average. Larger differences are observed studying the formation of shock shells during Coulomb explosions.