Simulation of the expansion of an ultracold neutral plasma.

We report the results of simulations that explain many properties of ultracold neutral plasmas. We find that three-body recombination is important at very low temperatures since it is a heating mechanism for the electron gas and it preferentially removes the slow ions from the plasma. We also find that collisions between cold electrons and Rydberg atoms are an important source of electron heating and deexcitation of atoms formed in the plasma. Simulations show that the Coulomb coupling constant does not become larger than similar1/5 for the reported experiments.