Positronium: Theory Versus Experiment

We have collected all known theoretical contributions to the energy levels of positronium and present a complete listing for the states n = 1, 2 and 3. We give the explicit dependence of the energy levels on the quantum numbers n, L, S and J up to the order R∞α3. In the next higher order R∞α4 only the contributions to S- and P-states are completely known. The annihilation rates of para- and ortho-positronium are completely listed up to the orders R∞α5 and R∞α6, respectively. We compare calculated values of energy levels and annihilation rates with experimentally observed quantities.