Excitation and delayed annihilation of Ps in a laser field

Resonant excitation of Ps to the higher P states is found to influence strongly the probability of gamma emission by annihilation. A considerable population can be, at the same time, transferred to the upper states. Numerical results for the excitation of the 2 1P and 2 3P states and the annihilation of the 1 1S and 1 3S states are presented for a number of field strengths of interest.