Experimental observation of ion correlation in a dense laser-produced plasma.

We present what we believe are the first experimental observations of ion correlation effects in a dense plasma. The plasma is produced in aluminum by colliding shocks driven by high-power laser beams. Computer simulations suggest that a peak temperature of over 1 eV and densities of several times solid are produced. Short-range order within the plasma is observed by means of the extended x-ray-absorption fine-structure (EXAFS) spectrum of the aluminum K absorption edge. Densities measured from the EXAFS spectrum are in reasonable agreement with the computer predictions.