Laboratory Studies of low density matter Original Research Article

A very brief summary of our current research on clustering in low density matter formed in near Fermi energy heavy ion collisions is presented. At the lowest densities and temperatures large alpha mass fractions are observed. Temperature and density dependent symmetry free energies have been derived from isoscaling analyzes of the yields of nuclei with A = 4. The symmetry free energies are far above those obtained in common effective interaction calculations, reflecting cluster formation, primarily of alpha particles, not included in such calculations.