Ion charge state distribution in the laser-induced Coulomb explosion of argon clusters

Abstract

Ion emission resulting from the Coulomb explosion of highly charged Ar_{40 000} clusters is studied experimentally and by means of three-dimensional microscopic particle-in-cells (3D-MPIC) simulations, for laser intensities up to 10¹⁶ W cm^-2. The experimentally measured ion emission spectrum shows a pronounced knee-like feature which defines the maximum energy of isotropically emitted ions in the Coulomb explosion. The variation of the 'knee energy' with laser intensity that is measured in our experiments is rationalized using 3D-MPIC simulations. The computations also enable an estimate to be made of the ion charge distributions. The computations show that at a laser intensity of 10¹⁶ W cm^-2, more than 64% of the ions that are produced are in very high charge states (8+ or higher).