Induced decay of positronium and grasers

The differential cross section and the total cross section for the stimulated decay of positronium by an incident photon of frequency ω is calculated as a function of the dimensionless variable xi = hω/mc2. For xi >> 1 the total cross section is found to decrease as xi-2. The particular case of positronium in a black-body radiation field is also examined. Expressions for the number of induced annihilations per second as functions of the dimensionless ratio mc2/kT and the number of positronium atoms are obtained. It is found that this rate is proportional to (kT/mc2)2 for kT <= mc2 and to (kT/mc2)1n(kT/mc2) for kT >> mc2. The possibility of utilizing induced two-photon decay of positronium as a γ-ray laser at the wavelength lambdasub(C)/2 is examined, where lambdasub(C) is the Compton wavelength. (author)