COULOMB EXPLOSION OF Ar CLUSTERS IRRADIATED BY AN INTENSE FEMTOSECOND LASER FIELD

Abstract

We study the rare gas clusters (Ar, Pb and K), containing 5.107 atoms per cluster, irradiated by an intense femtosecond laser pulse (Ipic ≈ 1018 W/cm2). The irradiation of these clusters by the intense laser leads to high excitation energies which are the source of energetic electrons, electronics emission, highly charged and energetic ions and fragmentation processes. For the study of different mechanisms of ionization of the cluster, we have used the nanoplasma model proposed first by T. Ditmire et al.[1] In this model, we consider a cluster with a radius of a few nanometers irradiated by a linearly polarized intense laser field. The dimensions of the cluster are much smaller than the laser wavelength (λ ≈ 400 to 1000 nm). The model treats all ionization mechanisms: heating, electronic emission and the expansion process of the cluster. The goal of our study is to investigate in detail the expansion and explosion of the cluster and to study the different factors leading to the final explosion. We have found that the hydrodynamics pressure is larger than the coulomb one which is not the case in the previous work.