Stimulated Annihilation (IMAGE) Joint Quantum Institute Caption Schematic of the stimulated annihilation process in the positronium gamma-ray laser. Time sequence of frames, running top to bottom, suggests how some "seed photons" from spontaneous annihilation of a few Ps atoms will stimulate subsequent Ps annihilations, resulting in a pulse of 511 keV gamma rays Credit JQI/Schewe Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.