Excitation of the positronium 1 /sup 3S/ 1 - 2 /sup 3S/ 1 two photon transition

This chapter reports details of the first experiment to excite optically Ps from the n=1 triplet ground state to the 23S1 state. Discusses the positronium source, the light source, and the experiment. Points out that an improved laser source and better laser metrology should enable a measurement with a precision comparable to or better than the hydrogen 1S-2S measurements. Improvements include a flat Fabry-Perot interferometer inside the ultra high vacuum chamber that will filter the laser output to create a nearby Fourier transform limited pulse, and precision laser metrology techniques using well known iodine and tellurium reference lines