Equilibrium contact probabilities in dense plasmas

Nuclear reaction rates in plasmas depend on the overlap (contact) probability of the reacting ions. Path-integral Monte Carlo calculations are used here to determine these contact probabilities, g(0), for one-component plasma (OCP) with emphasis on many-body quantum effects which can lead to order of magnitude changes. An intuitive explanation for these effects is presented. The small r behavior of g(r) for quantum systems and the relation to free energies is then derived and compared to the path-integral results. Going beyond the uniform background approximation, electron screening effects and the limits of the constant energy shift approximation are discussed. Thermodynamic properties for the quantum OCP are analyzed in a final section.