A non-uniform charging scheme to decipher charge state propensities measured in nano-cluster ionization

In this paper, we present an experimental study of charge propensities formed when Argon clusters are ionized with laser pulses of intensities up to 4 × 10 18 Wcm - 2 . The mean cluster size is varied from 1400 to 36,500 atoms to probe changes in ionization propensity at a given laser intensity. We attempted to use the Uniform charge scheme (that was earlier successful in fitting the ion energy spectra) to fit the ion charge state histograms. The difficulty in fitting the measured charge histograms compel us to adopt a non-uniform charging scheme to fit the measured ion charge propensity. Three different empirical weight functions that represent the charge of atoms in different shells of the cluster are used. The parameters of the empirical functions are optimized by least square fit to match the measured ion kinetic energy spectra. The weight function represents the terminal charge states of the ions coulomb exploded from the cluster and gives a better insight into the Coulomb explosion of the charged nanosphere.