Fluorescence measurements of expanding strongly-coupled neutral plasmas
  We report new detailed density profile measurements in expanding strongly-coupled neutral plasmas. Using laser-induced fluorescence techniques, we determine plasma densities in the range of 10^5 to 10^9/cm^3 with a time resolution limit as small as 7 ns. Strong-coupling in the plasma ions is inferred directly from the fluorescence signals. Evidence for strong-coupling at late times is presented, confirming a recent theoretical result. 
E. A. Cummings, J. E. Daily, D. S. Durfee, and S. D. Bergeson