Efficient Production of Rydberg Positronium

We demonstrated the efficient production of Rydberg Positronium atoms using a two-step incoherent laser excitation process. The two step process occurs first to the 23P state and then to the quantum numbers ranging from 10 to 25. We found a 90{\%} efficiency going from the 23P state to the Rydberg levels and an overall conversion efficiency of 25{\%} of the production of Rydberg atoms. This high efficiency is due to the overlap of the laser bandwidth with the Doppler broadened width of the 1s-2p transition and the suppression of the stimulated emission back to the 2P states, due to the intermixing of the Rydberg state Stark sublevels. By demonstrating the production of long lived Rydberg Ps atoms in a high magnetic field may make it possible to perform gravitational measurements of free falling positronium atoms.