Efficient positronium laser excitation for antihydrogen production in a magnetic field

Antihydrogen production by charge exchange reaction between positronium Ps atoms and antiprotons requires an efficient excitation of Ps atoms up to high-n levels Rydberg levels . In this study it is assumed that a Ps cloud is produced within a relatively strong uniform magnetic field 1 T and with a relatively high temperature 100 K . Consequently, the structure of energy levels are deeply modified by Zeeman and motional Stark effects. A two-step laser light excitation, the first one from ground to n=3 and the second from this level to a Rydberg level, is proposed and the physics of the problem is discussed. We derive a simple formula giving the absorption probability with substantially incoherent laser pulses. A 30% population deposition in high-n states can be reached with feasible lasers suitably tailored in power and spectral bandwidth.