The lifetime of Positronium has been measured to be about 142 ns (Nico et al. 1990), and its' ionization energy is about 6.8 eV. It appears to undergo self-annihilation thereby generating high energy photons. Hydrogen, by comparison, has an IE of 13.6 eV, double that of Positronium, but it does not annihilate itself, and has, in effect, an infinite lifetime. The radii of the two systems are effectively the same. When we shoot a beam of electrons at a beam of positrons we also get annihilation, but when we shoot a beam of electrons at a beam of protons, we get hydrogen atoms. I would appreciate any insight on the differences in the these two systems that explains the radical differences in behavior. Thanks in advance!