Dynamic light scattering fluctuation analysis for structural phase characterization in disordered dusty plasma

Abstract

Dusty plasma provides an excellent setup for studying strongly coupled Coulomb systems such as plasma crystals and plasma liquid. Based on coupling strength measured by the ratio of Coulomb electrostatic energy and thermal kinetic energy, dusty plasma can be tuned to form soft-condensed matter under moderate laboratory conditions. A standard approach to investigate uniformly ordered structures in dusty plasma is to use the inter-particle position dependent pair-correlation function, g(r). However, for non-uniform ordering of dust particles, mainly due to inhomogeneity in size and charge of the dust, the pair-correlation function is often highly noisy and difficulty to interpret, even though one could visually observe local spatial ordering in the dust particle configuration. In this study, we introduce fluctuation analysis technique based on fractal and wavelet approaches for extracting useful parameter, which, in turn can be used to characterize the structural phases in disordered dusty plasma. The Hurst exponents are determined for temporal light scattering intensity fluctuation at different neutral Argon gas pressures. It is shown that fractal exponent or Hurst parameter Hparameter can be used to describe structural complexity observed in disordered dusty plasma with inhomogeneous particle properties.