Dipolar interaction in a colloidal plasma
The dipole-dipole interaction between macroscopic grains in a plasma is calculated. The presence of a plasma medium shields the Coulomb grain interactions as well as necessitates that nonzero temperature effects be accounted for. The resulting electrostatic but not so much the Helmholtz free energy shows overshooting when equal strength parallel dipoles align with or are perpendicular to the line joining their centers. More striking is the appearance of a short range attractive well interaction for angles near pi/3. The contribution of the dipole-dipole to the total interaction in so-called plasma crystals has become increasingly recognized.
Resendes
DP
Centro de Fisica de Plasmas, Instituto Superior Tecnico, 1096 Lisboa Codex, Portugal.